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.

The marker to indicate where the user will drop an existing grouping column is shown at the begin and the end of the group column connector between groups:

Because the connector is very small it is not clear to new users where the column is dropped when it is dropped on the connector.

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#WLzO_nt1Pk2CZYPPIITYgA