To improve the performance of your application you can load the data from XML in DataTable and bind to RadGridView control directly and copy the data to additional DataTable. Another solution is to serialize data to some binary stream and then load to IBindingList<> collection and bind this collection to RadGridView control.
I hope this information is useful. Let me know if you need further assistance.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.