I've been using Telerik for years with past products and their frameworks have always been relatively solid. There's a reason they won many awards for being the best at what they do.
They don't look as fancy standing still as some of their competition, but they tend to be pretty darn stable, work as intended, and fix bugs rapidly. Working in practice is more important to me than having a fancy sales pitch. The fact they have a local branch local doesn't hurt either.
I'm considering using one of their frameworks for future drag and drop functionality.
If you don't mind, please go to this page - http://demos.kendoui.com/web/dragdrop/area.html
and tell me if it works as expected. If this basic test doesn't past muster, I'll look other places. If it does, then I'll continue with deeper tests.
You should be able to drag a ball to the two target areas. When the ball is over one of the two target areas, the text should change to indicate that. When the ball is moved to the target area, the text of the target area should change and the ball should return to its original position.
The load time should be negligible as well. I don't like our current load times and want our new development to be faster.