The leaked SP1, which I hope is *NOT* the final build, seems to bring with it an unwelcome issue on my machine the two occasions I installed (and uninstalled!) it.
Initially, I couldn't get it to install at all until I discovered, through some crafty Google-ing, that using an earlier version of Driver Sweeper when I upgraded from HD 5870 CrossFireX to a GTX 580 removed some backup files in the Windows\Winsxs folder. Without those files the SP1 installer aborts. Fortunately, I was able to reinstate the files without reinstalling Windows 7 from the Phyxion.net site and proceeded to install the service pack.
Everything appeared to go well and 20 minutes later (gotta love those SSDs!) my PC rebooted to report that SP1 had been successfully installed. However, when I tried to play DirectX 9 games such as Dead Space 2 or Need for Speed: Hot Pursuit they kept crashing to the desktop during the initial load. The Event log reported the error was with Nvd3dum.dll, apparently an NVIDIA driver file. DirectX 10 and 11 games though loaded and played fine. Odd, right?
Despite reinstalling the DirectX Redistributable (June 2010) and my graphics drivers (then v266.58) the DX9 games continued to crash. I had no option but to uninstall SP1 which allowed me to again play all my games with no issues. I even tried reinstalling SP1 again a few days later after I'd installed the latest v266.66 drivers (using a modifed INF file) but I got the exact same crashes. As you expect I uninstalled it... again.
I've no idea why SP1 causes only DX9 games to crash but clearly whatever hotfixes/updates it includes, one (or more) of them causes a conflict. I just hope that the official release doesn't have this issue. I do use third-party software though such as MSI Afterburner and D3DOverrider so perhaps one of those is incompatible with SP1? Whatever, I'll wait until the 22nd before I try SP1 again.