We've move to a model where we do pre-releases way more often than we used to.  The downside is that they are still really big and it can take a lot of time to do downloads.  Brian Keller recent wrote a post about how to minimize the difficulty and time spent downloading.  Read here for more info...

 http://blogs.msdn.com/briankel/archive/2007/09/06/a-more-reliable-and-faster-download-experience-for-rosario-vs08-vpc-s.aspx

Brian