We recently added row group functionality to our grids and we and our users are very happy with this.

Only thing that bothers us is the drop functionality on the grouppanel. We have an wish to make the drop functionality of the grouppanel much more intuitive. Especially when the RadGrid is already grouped on multiple columns.

Possiblity to drag a new, not grouped yet, column to the grouppanel to the position/order where you want the grouping of the grid to come up with. E.g. drag the next column between the first and the second grouping column. It is not possible to add it at a specific location.
 

 this case can be reproduced on the RadGrid Grouping demo on your site:
 http://demos.telerik.com/aspnet-ajax/grid/examples/functionality/grouping/grouping/defaultcs.aspx

Forum reference: 
http://www.telerik.com/forums/grouppanel-column-drop-and-reorder#GEEn16H44Uia4_U3_o143g