The grid has a number of built in filters, what is not supported is searching for cells that have no value or some value (i.e. NULL or NOT NULL).
This would be a very useful addition.

I'd like to see an event for Grid contents modified (after-edit or after-add/delete, etc).  This would enable a sync with a DataSource, for instance, without further user action.  Presently, this is not easily achieved.

It should be possible to change the width of a grid after it created.
http://www.telerik.com/forums/change-column-widths-after-grid-created

Add Min Width Property to Grid Column so that a user can't manually shrink a column beyond a certain width.

The event args from column.groupHeaderTemplate (and groupFooterTemplate) should contain a function to retrieve the data for that group. Currently, they only contain "field" and "value." If you made the grouped rows available in this event, clients would be free to add multiple aggregate columns of the same type (i.e., get the "sum" of multiple values instead of being limited to a single value). I've been able to halfway implement this, but it only works correctly if I'm only grouping by one column. For example, if I'm grouped by WidgetName and then by ProductCode, my event args for ProductCode should contain a function to return data rows for only rows matching the current ProductCode and WidgetName.

Currently we do not have the ability for descending to be first. It's either one, both in the asc/desc order, or none. You can changed the setting in the kendo javascript file but it'd be useful to have it be a property.

http://www.kendoui.com/forums/ui/grid/pager-controls-should-be-hidden-when-total-results-is-less-than-the-pagesize.aspx

Excel-like filter always show all available options.
When one filter was already applied  - could we limit number of options to see only options that are left after previous filtration?

We should be able to filter only by already filtered rows.

As alternative - could we have some event on Excel-like filter to populate options for it every time it expands?

Currently we use batch editing in the Grid control. The idea of batch editing is all changes are retained client side until the user presses the save button. 

When editing a cell a red dirty indicator is placed on the cell. This gives the user an indication that there are unsaved changes. however, when deleting a row, the row just goes away. There is no indication the user must still save. 

I would like to see rather than the record immediately removed a class applied to the row so we can apply some style like a strikethrough or red background color to indicate a pending delete. Also, we would be able to switch the "delete" button to an "undo" button.

Currently Kendo UI grid don't have any way to know that grid changes its mode from edit to view in case of incell editing.
As per thread (http://www.telerik.com/forums/is-there-any-way-to-know-grid-edit-mode-changes) we have to add blur/focusout event handler to know changing mode. But some time it happen (in case of adding custom widgets through columns editor) that blur/focusout event triggered but still grid is in edit mode.
Its better to have an event when grid changes its mode from edit to view so that we can minimize issue mentioned above.

Currently if you add a row to a grid in batch edit mode any rows that have already been edited will lose their dirty flag indicator.  I would like for Kendo to handle maintaining the dirty flag for these rows.  If there is a performance concern with adding this functionality, then maybe there could be a setting to turn it on or off.

include checkbox-based selection in the grid and allow the persisting of selections in paginated grid (i.e. user selects rows on page 1, switches to page 2, returns to page 1 --> previous selection is restored)

Very often in grids we want command buttons disabled (or not even visible) depending upon model data, such as Delete not being available if the data has certain values set. Something like:

columns.Command(commands => {
  commands.Edit();
  commands.Destroy().VisibleIf(model => model.IsPosted)
  });

Using HtmlAttributes would be acceptable if it was easy to access the model. I'm currently achieving this by using a client template and rendering the buttons myself, but this seems overly complex for what is a simple occurance.

Allow customisation of the bool filter in grids.  I.E. implement the UI property that works for other non-checked columns.  The current filter is too wide, does not allow fontawesome characters, etc.

I was working with Sencha ExtJS and they have to option to make components "stateful" (http://docs.sencha.com/extjs/6.2.0/classic/Ext.state.Provider.html). This will safe user modified settings in browser (defaults to cookie but you can provide your own implementation).

Example (for grid):
* we specify width=100 for first colum
* we allow users to resize columns
* If a users resizes a column the new width will be stored in state
* ... if the user later opens the page again, values from state will overwrite "defaults" from code.

If we use this for column width, visibility and order we've a perfect customizable grid view.

My users ask for this in almost every application.  When a grid is grouped, the users want to see the groups in an order that indicates some ranking by an aggregate value. For example, If SALES-DETAIL table is grouped by SALESPERSON, the default alphabetic order of the groups might be AMELIA, BARBARA, CARLOS, DAVID, HARRY, THOMAS, ZELDA. But users want to see the groupings in descending order by the salesperson's TotalSales, which might be HARRY, ZELDA, AMELIA, THOMAS...etc. So we need a way to specify a custom-group-sortorder. And to be perfectly clear, that is the sequence of groups with respect to each other, not the order of detail data inside the group. The detail records might be sorted chronologically by SalesDate regardless of the order of the group relative to each other. In SQL the equivalent would be  ... GROUP BY SALESPERSON ORDER BY SUM(TotalSales) DESC(ending). This feature would work hand-in-glove with another requested feature, showing the group footer when the group is collapsed.

The refresh button availability should be indepent from the grid being pageable. The user may want an updatable grid without having page navigator.

Right now there is a progress indicator that shows on the grid when the data is being read.  Could this indicator also be shown during save operations?  Right now when you save there is a brief delay while the save operation is taking place where to the end user it looks like nothing is happening.

The End-User experience for multiple column sort is awful. Please provide a UI that lets them see & change the columns they are sorting by. 

Current problems are: 
1. If the user is sorting by 3 columns. All they see is 3 columns with an up/down arrow. There is no visual indication of the actual sort order (Col1, Col2, Col3) or (Col2, Col3, Col1). 

2. Lack of Control.
This gets more confusing if you have 3 columns in a sort, then  click Col2, until it is not sorted. Then click it again to make it sort ascending. I assume it drops out of the sort, & is then added at the end. Making sort =  (Col1, Col3, Col2). 
This confusion forces you to clear everything & start the sort again. 

3. Inability to clear quickly. 
But there is no UI that offers the user a quick way to Unselect all sorted cols, so they can start the sort selection process again. Clearly we can add something to the toolbar, but ideally they wouldn't need to clear & restart their sort selection. . 

4. Unpredictable outcome.
It is not obvious to the User how to control the order of the multi-column sort. How does the sort get determined? :-
A. First column selected becomes the Primary order, the next col is the Secondary order. 
	eg: select Col1, then col2, then col3, to get (Col1, Col2, Col3) order. 
OR
B. Last column selected is the Primary. 
	eg: select Col3 then col2, then col1 to get (Col3, Col2, Col1) order.

5. Server/Database cost. 
Sorting & network round trips are expensive. Toggling from Asc / Desc / Clear. Is expensive & slow compared to setting all the columns once & clicking OK. 

6. I'd add a mockup image, but this feedback screen doesn't permit uploads. To get an idea of a potential UI, Try sorting on multiple columns in Excel. It shows like a tree, with the primary key at the top, the secondary a line lower, followed by the less significant keys below it. 
OR at min. Change the Arrow into an Arrow with a tiny number (1,2,3 etc)
7. The current approach you use to add the Sort icon is really annoying to the user, especially when they have many narrow columns of numbers. Be aware that when you add the sort icon, converting a Label into something with 3 "..." chars is unnecessary. We found it cleaner to just truncate the chars that didn't fit, the user gets to see 2 more letters of the label. Which may be enough for them to know which column it is. And it is obvious that the column was too small to display more text. 
The large padding to the left of the "ColumnMenu" icon is part of the problem, it could be much smaller. 0.5 to 0.25 char width is sufficient. 
We did a lot of usability testing around this for a different control. The outcome was nearly unanimous in favor of the change above. 

PS: I too could see benefit in having the sort indicator display to the left. But the changes above may reduce the need a bit..

Please add out of box functionality ( MVC and Kendo ) for simple search panel like DevExpress : 
http://demos.devexpress.com/MVCxGridViewDemos/Filtering/SearchPanel