Don't be fooled - despite being tagged Beta, this actually isn't a Google product. I kid, I kid!
Hopefully by now you've already seen Brian's list of SP1 improvements for TFS. My work's been mainly around SQL Server 2008 support (it's been interesting), although my team did have one brown-paper-bag bug where tfsadminutil sid /change didn't work. At all. A one-line fix, at least :)
Anyway, I noticed ScottGu posted a list of improvements for the rest of the service pack. Wow.
This particular bit made me very happy:
I use all 4 of those listed in various ways on my own asp.net 3.5 sites, and it's great to see this! It'll make development that much easier.
Also, I'd been using Dynamic Data support already, but it's nice that it's in the service pack so I can avoid the separate download.
I need to learn more about LINQ-to-Entities to see if it has anything compelling over LINQ-to-SQL (which I've happily been using). Astoria's interesting, but I don't have any need for exposing data as REST at the moment, so it may be awhile until I get around to playing with that.