Looks like Vista SP1 will be released on February 15. I have tried out the release candidate and Vista seemed to work a little faster so hopefully there will be even more improvements in the final.
Source:Engadget
The first service pack for Windows Vista is on its way, and PC Magazine has a preview of an early private beta version.
After months of speculation, rumor, and silence from Microsoft, the company is finally talking publicly about Service Pack 1 for Windows Vista.
Microsoft says that the first public beta of Windows Vista SP1 will be available in the next few weeks to TechNET and MSDN subscribers.
Microsoft is set to release the first beta of SP1 for vista by mid-July and release the final Vista SP1 in November 2007.