Finally, it is released and available at http://msdn.microsoft.com/vstudio/support/vs2005sp1/.
As it looks like, not all of the bad stuff got fixed in this SP release, but apparently – development will get a bit more easier.
Also, you can see that there is a link over to the beta of Visual Studio update for Windows Vista. Though, at least for now, this link points to nowhere ("The download you requested is unavailable"), but I’m waiting for it as I am using Visual Studio on Vista already for a while.
To keep things short – I like developing on Vista.