Though I'm already quite familiar with ASP.NET I'm just now starting to experiment with ASP.NET AJAX for real. I did some testing with the early alpha's about a year ago.
After installing the Extensions (RC1) and the December CTP I also downloaded and installed the samples to get a look at how it could work. I started with the SimpleList application and after copying the assemblies Microsoft.Web.Preview.dll and System.Web.Extensions.dll I soon found out that the webform 2_SimpleList_AutoComplete_DragandDrop.aspx doesn't really behave that great. So I did some digging around and I soon found out that the web.config wasn't entirely correct. I added the following parts:
25 <add name="dragOverlayPosition"/>
92 <profileService enabled="true"
94 writeAccessProperties="dragOverlayPosition" />
And now the application works like a charm.
Now I hope to find something in ASP.NET AJAX like drag & drop and auto updating of where an element was. Just like the demo of script.aculo.us' shopping cart. Hmm, guess I still have quite some learning to do.