Having a RadGrid in batch mode with Master and Details tables, when you add a new master record, you are not able to add a new detail record until you save the master record. 
This feature should be built in the RadGrid.

Natural Sort-Option for RadGrid to sort the items in the grid in a natural way. By natural sort we mean sorting like StrCmpLogicalW (Win32 API).

Having Paging enabled, the Column Aggregates should be calculated based on the data from all of the group's items, even if the group is spread over several pages.

Currently, only the data from the visible items on the current page are calculated. 

This behaviour only occurs in Chrome Webbrowser if you select an item in the grid in the bottom area of a list which has of more than 20 elements.
If you start to drag the item, it appears far to low which means that it is sometimes not on the page anymore.
It is even possible to redo this with the telerik demo ( on http://demos.telerik.com/aspnet-ajax/grid/examples/columns-rows/rows/drag-and-drop/defaultcs.aspx)
if you use the pager some times.

It is possible to have "{4} | Page {0} of {1}, items {2} to {3} of {5}" (all 6 parameters) for PagerTextFormat, but not just "items {2} to {3} of {5}".