I've been using VS2008 Team System Dev Edition since it hit MSDN, and it improves on 2005 in almost every way, although not necessarily that much. C# 3.0 and LINQ are definitely the best things about it, and Team Build in TFS is a lot better (read: usable).
As you say, though, the stuff I really want remains "H1 2008":
ADO.NET Entity Framework, which will do the things I need that LINQ to SQL doesn't;
Parallel FX, especially the Parallel LINQ which will make multi-core support a breeze;
ASP.NET 3.5 Extensions, especially the MVC Framework;
SQL 2008 and the Sync Framework, so I can stop faffing about with SQL 2000's appalling merge replication;
Windows Server 2008, although (waiting upon waiting) that'll be of even more interest when they add ASP.NET support to the Core Web Server.
There's also the vague promise of Rosario, the assertedly much-more-improved Team System, although my cup runneth over so much I haven't even downloaded the CTP for that yet.