I had 2007... very bloated and confusing interface. For me, Office 2003 remains the best. I don't like 2007's ribbons interface.
Eh I don't like either I'm only using microsoft office 2007 because of a college course I'm in and the teacher wont let me use open office or i'd be using that
I use 2007 Enterprise. I love it; IMO, it's better than 2003... but it is mainly a personal preference. I really enjoy the new interface.