The format specifier 'tt' in the ExcelExportFormatString property should be outputed as 'AM' or 'PM'.
For the formatting to work correctly the users have to set the property to Excel format codes not .NET format strings.
Here is the list of excel's format  codes: http://office.microsoft.com/en-us/excel-help/number-format-codes-HP005198679.aspx

SortDescriptors does not apply when they are added to control with no DataSource defined and no rows added. The added rows from the user are not sorted.

FIX. RadGridView - cannot show tooltips in GridViewComboBoxColumn, while in RadDropDownList the tooltips work correctly

1. Create a new project containing RadGridView
2. Set a DataSource
3. Set a ColumnGroupsViewDefinition
4. Apply grouping
5. Do all this on a button click
6. Run the application and click the button.

The RowForeColor property of a conditional formatting object does not apply to the column which the condition is defined for.

ADD. RadGridView - add kitetic scrolling support

If you show a hidden form that hosts a RadGridView control instance, the filtering does not perform correctly.

After updating a cell, the RowsChanged event fires 3 times

If two conditional formatting objects apply to the same cell and the cell meets both conditions, the settings from both of them should apply to the cell (if they do not apply to the same property).

Add option for alphabetical order of the columns in the "Rule applies on:" drop down list.

1. Add a RadGridView
2. Create a new method and call it on a button click
2. Create and set a ColumnGroupsViewDefinition
3. Add rows in unbound mode

Currently the editor cannot be closed using the CancelEdit method when handling the CellValidating event.

FIX. RadGridView - setting the grid to ReadOnly and then back to normal mode, does not show the AddNewRow

One may want to perform a search operatior over the records of RadGridView instead of filtering them. The search should be incremental and should scroll to the first position that contains a record that matches the search criteria.

The issue appears when the current column of the control is changed programmatically in a way that the RadGridView's horizontal scrollbar value needs to be positioned between its minimum and maximum value.

FIX. RadGridView - header cells incorrect state when column grouping is used. The clicked cells remain Hovered even when the mouse is not longer above the cell.

ADD. RadGridView - add the ability to group by a certain column and display the groups sorted by the values of another column

FIX. RadGridView - composite filters does not work

The GetLookUpValue method of GridViewComboBoxColumn throws exception when the column shows enum values.

FIX. RadGridView - FilterButton for Excel-Like filtering of GridViewComboBoxColumn, shows incorrect ToolTipText