Yes, I know that you know that Update Rollup 8 for Exchange Server 2007 SP1 has been released, but I just wanted to remind you. You can find more details here.
If you wonder what the release schedule is for Rollups, it usually is about 8 weeks. You should really make Rollups part of your patch management strategy as they are released on regular release cycle and includes fixes for known issues and bugs fixed between Rollups.
While you are at it, don’t forget to check out Exchange 2007 Service Pack 2 announcement.