I somehow missed this in the flurry of activity this week, but Service Pack 2 for Windows Vista and Server 2008 is now available on MSDN and TechNet, ahead of the "sometime in May" date that Microsoft previously promised. (It arrived April 30 for the pedantic.) Inconveniently, there's only a single version of the SP2 installer, and because its for x86, x64, and (yes, seriously) IA64 (i.e. Itanium) it's kind of huge. Presumably, we'll see different versions of this over time, including those that have been slipstreamed into both Windows Vista and Windows Server 2008.
The download servers seem a bit quicker today too, which should help.