ACP magazine have done a test-case on the RTM (Release To Manufacture) version of SP1 for Vista, and contrary to a lot of the speculation I've been reading in the press to date, guess what - it actually has improved performance! :-)

It is interesting in the article (follow the link), the difference found between a clean built RTM Vista machine that has incremental patches applied (as most of us have done over the last year or so), versus one that is clean built and then has SP1 applied before any other patching. It seems that the more "holistic approach" of the service pack provides a better experience, and cleaner results than the bolt-on nature of patching, which isn't much of a surprise, but it's nice to see someone's finally tested the theory.

Vista SP1 up to 86% faster | APC Magazine