Microsoft has released a beta version of SP1 for Team Foundation Server through Microsoft Connect. In SP1 there are a lot enhancements to the system, specially when it comes to performance. The TFS team has updated a lot of the sprocs dealing with version control, workitem tracking and the datawarehouse components.
In this post, Brian Harry has listed some (if not all) of the bug fixes in TFS SP1. Check it out if you have time. Also, go and sign up to get SP1 (for both TFS and VS2005) and try it out...hopefully on your TEST TFS box!