I have been useing exch2003 for about a year now and i am happy with it, ya it was a little work moving from 2000 to 2003 but its all good. It was more work moving from 5.5 to 2000. I made the staff write down anything they needed emails addresses what ever so it wasn't so tough on me, they lived through it, some were not happy, but you can't please everyone.
