Grant just sent the mail, 2040 is the SP1 CTP build. Now this post will not appear until tomorrow at 6am so I don't know for sure but the build should be available here a couple of hours after I write this (16:00 Pacific Mar 15).
As with all SPs there is lots of little stuff, some you may have hit some you may have not, but the big news is that Database Mirroring will be supported in production with SP1. We made changes based on the feedback we got during the RTM CTP process, we have also been working privately with customers(~50) in advance of this CTP to get their further feedback. One of the pieces of feedback was the desire for a Monitor UI to get an overview of whats going on, well thats part of the CTP so enjoy.
This will likely be the only CTP for SP1 so get us the feedback as soon as you can.