I would like to suggest that a more intuitive clear filter option be used on the Filtering columns in the RadGrid.  Currently, I have to select "No Filter" from the Filter list of options.

Instead, I believe the Filter should be provided to be more intuitive similar to other applications such as Microsoft Access, Excel or Google Search.

In Microsoft Access or Excel, I simply unselect the Filter icon to remove the Filter.
In Google Search, I simply click the X icon next to my search criteria to remove my search text.

Either of these methods should be adopted so that the overall end user experience is more pleasant and comparable to filter capabilities in other tools and products.

When the grid has no paging and all the groups are collapsed its good to have a paging defined within grouping to display all the groups in the same page as well can browse through the items within the group with paging defined.

As per the current implementation of the RadGrid control, if we set the CurrentFilterFunction, that will be used for that column and even with no value, the same filter function will be used (specified in the CurrentFilterFunction).

This is not user friendly and one should expect that "NoFilter" will be invoked when there is no value.

There is no possibility for invoking the "NoFilter" command when the following properties are set:
ShowFilterIcon = False and AutoPostBackOnFilter = True

please refer the following link for more information:
http://www.telerik.com/forums/filter-not-resetting-if-filtervalue-is-empty-in-client-side-filtering

Ability to add custom buttons to the command item collection. 

I brought this to Telerik's attention 4 years ago. The grid Pager is a poor location for the built-in loading image because it is not clearly visible in a number of scenarios. First off, it is small and tucked in the corner, which makes it hard to see. But there are other scenarios where it is completely invisible. 

If the grid height is fixed and larger than the screen size, the entire pager is not visible unless the user scrolls the window. So, the loading image will not be visible when users take actions like sorting/editing/deleting/filtering which tend to occur towards the top of the grid.

And, if the grid has Paging disabled, then the pager and built-in loading image will NEVER be visible.

I understand that one can add a custom loading image which would work better. And if asked, Telerik can provide a couple dozen lines of custom javascript which will move the loading image for a grid. But If your project has a large number of grids, adding code to each is untenable. And at the end of the day, this should be a built-in feature of Rad Grid, not something that needs to be hacked to work appropriately.

RadWindow used to have a tiny loading image in the status bar which was invisible in a number of scenarios, most notably when the status bar was disabled. The Rad Window team saw fit to move the loading image to the center of the Rad Window where it belonged. This was years ago. For some reason, the Rad Grid team has not seen fit to do the same. Why is the RadWindow team aware of and responsive to concerns about the usability of their control and the Rad Grid team is not?

Is any option to use RadGrid in disconnected mode. So when user lost connection with internet(intranet), he can continue to work with grid - add new record, edit records. In html 5 appear such technologies like HTML5 Storage,Web Sql. Is it any way to interact with them?

When doing batch edits on a grid if you delete a row, the row is no longer visible in the grid but it is not actually deleted until users click the 'Save' button. This has led to some confusion for our users who delete the rows then navigate off the page w/o pressing save. They think they successfully deleted the rows but when they return to the grid the rows are still present.

We have added logic when navigating away from the page that checks and prompts users if there are unsaved batch edit changes, but in case of deleted rows, when they look at the grid, there is no indication about the deleted rows so they are unaware that the rows were not actually deleted.

We like the idea of not deleting the rows until the user presses the save button, but maybe the delete action should not remove the row from the grid and instead simply strike it out, or put a 'marked for deletion' flag or do something visual to keep the row on the grid but make it obvious that it has been marked for deletion. This way users will not be confused and will know that they must click the Save for the change to take effect.

If the user's browser supports html5 local storage, I'd like for the RadGrid to be able to save/load its settings from there for things like page size, column order, sorting, etc.  Other controls may be able to do this as well.

For the time being you can add the following JavaScript workaround at the end of the form:

<script>
            Telerik.Web.UI.RadGrid.prototype.repaint = function () {
                if (!this.canRepaint()) {
                    if (typeof (this.get_element()) != "undefined") {
                        this.add_parentShown(this.get_element());
                    }
                    return;
                }
                else {
                    this._clearParentShowHandlers();
                }

                if (!this._scrolling && this.GridDataDiv) {
                    this._scrolling = $find(this.get_id())._scrolling;
                }

                if (Telerik.Web.UI.GridScrolling && this._scrolling) {
                    if (this._scrolling._shouldInitializeLayoutAndScroll) {
                        this._scrolling._shouldInitializeLayoutAndScroll = false;
                        this._scrolling._initializeDimensions();
                        this._scrolling._initializeScroll();
                    }
                    else {
                        this._scrolling.onWindowResize();
                    }
                }
                else {
                    if (this._repaintWidthFlag)
                        this.get_element().style.width = "";

                    var masterTableViewWidth = 0;
                    if (!!this._masterClientID && this.get_masterTableView() != null) {
                        masterTableViewWidth = this.get_masterTableView().get_element().offsetWidth;
                    }
                    if (this.get_element().offsetWidth < masterTableViewWidth) {
                        this.get_element().style.width = masterTableViewWidth + "px";
                        this._repaintWidthFlag = true;
                    }
                }
                if (this._masterClientID && this.get_masterTableView() && this.get_masterTableView()._virtualization) {
                    this.get_masterTableView()._virtualization.repaint();
                }
            };
        </script>

For RadGrid (and other similar controls) it would be nice to be able to simply add AutoHeight="true" to the elements markup to make the grid calculate the browser height and adjust it's own height (including the scrollable DataDiv inside it) automatically rather than having to resort to custom javascript to achieve the same thing.

ie: activate AutoHeight on RadGrid and simply set the distance from the bottom of the browser window to allow for footers, etc. and have that distance maintained even when the browser is resized.

Height and ScrollHeight can only use explicit values - not percentages - which is kind of useless if you want the grid to occupy 100% of the available browser height across different devices. http://www.telerik.com/help/aspnet-ajax/grid-height-vs-scrollheight.html