I'm going to have to disagree with you on the footprint for telerik.  When we were building the first release of Active CRM, we carefully evaluated every control suite we could fine.  It came down to ComponentArt and Telerik.  I have been a fan of the r.a.d. editor since the first day it was released.  However, it has become massive over the years.  Whether you have 5 buttons in your toolbar or all of them, the footprint is the same.   Before we released Active CRM, we actually created two versions of the application, one with ComponentArt and the other with Telerik.  We were testing for total payload for each request, processor utilization on the client and the server, rendering speed and total lines of code needed to accomplish each various task (i.e. datagrid, callback, treeview).  

DataGrid
Speed - ComponentArt
Payload - ComponentArt - (both controls produce a ton of client side code.  Compression helps)
Lines of Code - Telerik
Features - Tie

NavBar and Menus
Both products were pretty much equal.  ComponentArt was still a lighter control.

Tabs & Multipage
Honestly, I can't remember exactly the details for Telerik.  I will say that before you go creating a view with 7 tabs and pageviews you need to carefully consider if this is the best way to load your page.  If you choose the basic, default methods (non-ajax) you are basically creating 7 pages of content which will all load at once on the first load.

Callback - Testing stopped at this point.  Telerik could not load nested controls in their callback.
Speed - ComponentArt
Payload - ComponentArt
Lines of Code - ComponentArt
Features - ComponentArt

 All that being said, we have ended up writing our own controls.  We even replaced the ComponentArt CallBack with our own control due to limitations with dynamically loaded nested controls.  The only third party controls we use now are the ComponentArt NavBar and their new editor control.  Here is a link to a blog post I made almost a year ago about the ComponentArt grid.  
http://geekswithblogs.net/wmorgenweck/archive/2007/02/02/105242.aspx

If you are looking for speed and complete control of your data then all you need is a good callback control, the stringbuilder and a good old datareader. 

We also did a complete evaluation of web-based controls back in 10/07, and we chose Telerik.  Infragistics controls, IMO, were a disaster.  In fact, we had an enterprise license to the Infragistics controls, but couldn't even uninstall it--the uninstaller gave us errors, and we had to use registry cleaner and such to truly uninstall Infragistics.

When we compared Infragistics, ComponentOne, ComponentArts and Infragistics, it really wasn't close--for us anyway.  Mainly because we are looking for license freedom, support quality (heck, I finally received an email response from Infragistics in December--two months after we had completed our analysis), and the fact that all of the control companies needed to rewrite their controls to take into account ASP.NET AJAX and web 2.0 world, and Telerik was the only vendor advertising this fact. 

ComponentArts did have better performance than the current set of Telerik controls--can't deny that.

One last important thing we required--confirmed support for DNN.  It's interesting to see the default setup for infragistics mentioned.  What this does is create a virtual directory for the infragistics controls and samples to work.  We must have an earlier version, because just dropping them into the bin folder sure didn't work for us--and we couldn't get diddly for support from Infragistics for DNN as mentioned above.

I would say that if you went with ComponentArts (and aren't building code that you want to license) or go with Telerik, you can't go wrong.  We've been really pleased w/the level of support from Telerik...