This is very interesting to us, because we have actually been switching out Telerik controls and replacing them with jQuery UI and other jQuery based widgets. Not because we don't like Telerik controls (we liked them a lot), but because we really don’t like the MS ajax and the whole ASP.NET postback/viewstate mess.
It’s quite a bit of work for us to write back end .NET objects to match the various jQuery UI components, and we would rather pay Telerik to do all that for us.
Questions – does it require MVC? Does it require the MS ajax library?