I've had my DX for almost a week. I get better than expected battery life from mine. Running 2.2, stock browser, can facebook, browse, text, talk and go through my 12-14 hour workday and still have good battery (green). Had a little fun at work today with media player and pandora, so I finally managed to get down to about 20%.
I had a Samsung Moment that chewed through battery life ... was happy to get 4hrs on a full charge. Had a small problem with receiving calls.
I use the Battery Manager with Nighttime Saver Mode. Ditched a lot of widgets/app things I don't use or care about.
So far, very happy with my X.