Lest I be seen purely as a big fat winer ;), here's some of the really positive things I've noted in the MSAjax beta 1 release:
- Opera support (or at least, a commitment to it) - fantastic, Microsoft really listened to the community on this one
- Improved debuggability - much needed, spelunking through earlier Atlas CTPs in the debugger wasn't very fun
- Replaceable script library - again, oft requested by the community
- ScriptManager.EnablePartialRendering defaults to true - I never did understand why it was false originally.
- UpdatePanel client-side events - woohoo!
- Extender controls now look a lot more like regular ASP.NET controls - a good thing
I'm planning on digging into the beta a lot more over the next couple of weeks. More later...