WOW, so much misinformation on this thread. I am an Exchange admin and have been for 10 years. Exchange 2007 (despite the horrible management gui) is a fantastic product and is rock solid running on Windows 2008 Server.
I'll have to take your word for it, because I know no one running Exchange 2007. They're all waiting for Exchange 2012 or whatever. Upgrading every cycle is too expensive, from what the IT folks tell me (meaning in licenses, hardware, and training, as well as corporate downtime). Could just be an excuse, but it makes sense. 'Course, if Exchange 2007 is really the panacea of stability and reliability (although graybeards tell me they were told the same of 2003 ...) then it would pay for itself, as we lose big bucks with email downtime as it is!
How many Exchange instances out there are running the latest and greatest from Microsoft?