I bought an MPx200 early last month from AT&T, and returned it yesterday. It was a cool phone, and the *phone* side of things worked really well. I especially liked the contacts search interface.
Where the phone really fell down, though, was on battery life. Like you, I started out with ~24 hours of battery life, which was marginal but acceptable, but after a week and a half, this dropped down to only 8 hours. I could shut down the phone, kill off everything running on it, charge it, and leave it sitting on a desk, closed, with nothing running, and it'd be dead in under 8 hours. I swapped batteries at the AT&T store, deleted apps, removed my SD card, and nothing helped. So I returned it, and I'm going back to carrying two devices.