It's been a while since I posted but ran across an interesting video from Perry Clarke on some of the I/O changes that went in to Exchange 2007 and 2010. For anyone that doesn't know, Perry runs the mailbox team (Within the Exchange group) and has been there for a LONG time. I actually had an interesting discussion/disagreement with Perry back in 2005 during an MVP summit. This was prior to Exchange 2007 and they were just in the middle of some critical design decisions around Exchange 2007. One of those involved not including export to PST (as well as not extending Exmerge to use Unicode PST's) and the discussion got a bit heated as I pointed out many scenarios in our business (Legal) where we needed this feature. Needless to say, Microsoft added 'export-mailbox' to Exchange 2007 sp1 and everyone was once again happy.
Anyways, enjoy the video from Perry: