Should you install Vista SP1 beta?
that a beta of SP1 should be available next week. The question is should you install it? That depends on your situation.
Microsoft is including several feature fixes and is supplementing existing features in addition to a couple of security updates.
When Windows XP SP2 beta came out, some people installed it and some avoided it until the final version. While XP SP2 final was more stable and slightly redesigned, the feature set remained basically the same and some problems from the beta carried over.
Full article here: Source