I've enjoyed the MP games I've taken part in, although I haven't exactly had the most impressive results. It's a real change from the SP game, and with the fast pace it doesn't really hold the same sort of interest as a SP game. It's much more about building an army quickly than it is about building a civ to "stand the test of time." Most of the MP games I've taken part in last less than 100 turns which is pretty fast for someone who tends to SP on epic speed.
That being said, MP sessions are a lot of fun. And while it is disappointing to lose (especially if you get crushed) it's just as fun to win. And knowing you're playing against a real person rather than the predictable AI adds a lot of excitement and really gives you a lot to think about.