If you happen to be a developer with MSDN or TechNet privileges, you can now go out and snag the release version of Windows 7 Service Pack 1 and Windows Server 2008 R2 SP1.
The pack brings a lot of compiled minor bug fixes, security fixes, etc. Most of these have already been distributed via Windows Live. It's unknown whether the most critical components originally expected -- USB 3.0 support and Bluetooth/Wi-Fi performance improvements -- are present in the final build. As sources aren't talking about it, we'd be inclined to say that it doesn't seem likely they will be included at this point.
That leaves the only remaining big items in the pack as RemoteFX and Dynamic Memory -- items that you will really only care about as an IT user (which happens to be some of the users who will be getting the early edition of the update). RemoteFX enables 3D graphics in virtualized slim clients. And dynamic memory allows for pooling and efficient use of memory in a virtualized slim client setup.
For regular users, this won't be a super exciting update like Windows Vista SP1 or Windows XP SP2 -- unless some of the missing features show up.
The download should be available soon from the Windows MLVS Volume Licensing site in ISO format (for burning to DVD for fresh installs) and in patch form (for existing installs) shortly.
We'll let you know if we get any more details or if the any missing features (improved Wi-Fi, where art thou?) show their faces.
Windows 7 SP1 has been in public beta testing since June.