Stay away from Gmail
Seriously, I cant reiterate that enough.
I worked for a fairly modern Australian university that migrated from Exchange to Gmail while I was there. It was nasty. The test group were administrators and IT staff and I think a very small group of senior academics.
Turns out that Gmail simply doesnt have the flexibility or customisability that the university needed (for instance, Google limits the number of email addresses you can bulk email at once. They also limit the number of contacts you can have, or at least did at the time). The university was also too small to warrant any attention from Google (5000+ staff, 20,000+ students), so trying to get any issues resolved, or in some instances even investigated, was nigh on impossible (unless Google already had a first line support level write up for a known issue).
When they made the final switch, within weeks the service desk started to melt under the pressure and it never really let up, as we would resolve one thing only to have something else come up.