Most people wait for SP1 of a product to be released before deploying it. I’m not normally one of those people and I’ve been deploying Exchange 2007 now since March this year for a larger client of ours. I’ve currently got an open case with Microsoft on some funky intersite SMTP communications issues that has been going on now for 5 to 6 weeks. I was hoping that Exchange 2007 SP1 might resolve these issues, but reading of the release notes indicates that applying SP1 is a one way operation. So I’ll continue to investigate the issues with MS.
Anyway – having said all that Exchange 2007 SP1 is now out. You should most certainly read the release notes so that you know all the gotchas BEFORE you go applying it in your environments. You can get the release notes here and you can download the service pack from here. It’s an 800MB + download.