Finally some great news! Scott Gu officialy announced the ASP.NET MVC Framework on his blog. I'm so anxious to get my hands on the framework! If you're not familiar with MVC I would suggest reading Scott's post, he explains it briefly.

However there are some really cool features... for example you can use both MVC and WebForm frameworks. You can also continue to use Master Pages, ASCX controls, <%=%> snippets and plenty more. The MVC framework will not use the existing post-back model, instead you route all end-user interaction to a Controller (no viewstate or page lifecycle - a great approach).

What about ASP.NET AJAX UpdatePanels? Scott mentions this in his comments:

UpdatePanel does use postback, so you won't use that control directly within a MVC based view.  But there will be a control (and optional helper method) with capabilities very similar to it.  It will invoke an action on a controller and allow you to incrementally update a portion of HTML really easily.  It will enable you to use the ASP.NET AJAX libraries really easily.

Curious to see the "optional helper method."

My biggest frustration has been with the difficulty in mashing JavaScript with ASP.NET WebForm's rendered output. With the MVC Framework it seems like I'll finally have the control I want to use JavaScript frameworks and server-side controls seamlessly.