Well, I was just starting "from the top." For example, look at your "Installation and deployment" -> "Installing RadControls on your computer" section. In the "Which file do I need to install" page (http://www.telerik.com/help/aspnet-ajax/introduction-which-file-do-i-need-to-install.html
), there's no mention of your new "Control Panel" based installer. That's not really that big of a deal, it just created an initial stumbling block, "this doesn't seem to match what's currently available" kind of thing.
Moving on down, you see specific pages for Adding Controls to the Visual Studio 2008 Toolbox (and also for VS2010), but not for 2012. Or, specific pages for Using Intellisense in Visual Studio 2008 (and also for 2010) but not for 2012. Again, not a huge deal, it just added to the mental adjustments and "hmmm, more things that don't seem to have been updated" bit.
So as I mentioned, before I kept going on down the documentation, I was wondering if you had made a pass at updating this recently. I've noticed MANY nuances in going to VS2012 and .NET 4.5, so I think it warrants careful attention to new documentation!