As a TRUE ASP.NET AJAX Control
you have almost unlimited possibilities with RadGrid for ASP.NET AJAX client-side API.
I've spent ~ 30 minutes to create small and powerful demo with client-side data-binding to 1 mil. records
and LINQ. No traditional post back/ajax requests to the same page, no ViewState - just pure JSON
To see the traffic between client and server you can use FireBug, HttpWatch, Fiddler or any other similar tool. Here is a small screenshot from FireBug:
Enjoy! [Source code]