We get asked about what we're doing about AJAX quite a lot these days, especially about ASP.NET for AJAX (the technology formerly known as "Atlas"). We *love* AJAX. We actually use AJAX (albeit not ASP.NET for AJAX) all over the place in SharePoint sites. Dropdown menus when clicking on Edit Control Buttom (ECB) menus? AJAX. The Settings menu on a site's home page? AJAX.
As for ASP.NET for AJAX, we love it (we're ASP.NET developers ourselves – how could we not? J), we're excited to see Beta 2 emerge, but given that we started working on Windows SharePoint Services 3.0 and Microsoft Office SharePoint Server 2007 in late 2003, it wasn't possible to engineer those products to ensure 100% compatibility at RTM.
We've been investigating this issue very carefully. We've been working directly with the ASP.NET team to come up with the nicest possible way of giving you the ability to make all of this work. But we're not ready yet. We know some things work fine, other things will work fine once one or both of our teams have done some extra work, and a few (hopefully very few) things won't be supportable in SharePoint sites.
Until we're ready, though, we'd truly appreciate it if you let us work it out rather than trying to hack a solution of your own. It will take some time, but whatever we're able to work out will be something we can support.
Here's what we can say with confidence today:
Besides, you're going to have enough to get done with SharePoint Products and Technologies given that you can download WSS 3.0 on the 16th of this month, aren't you?