I've been using Miui for a week now (hands down the best rom) and I havent really had any bad battery problems
Tho I am using the extended battery I get a full days worth.
while I'm at work this is what I do, I usally turn the data off cause I get bad 3g there so theres no point to keep it on. Turn it on when I go on my breaks and stuff, then turn it on wifi when I go home, and at that time its at like 80-85%
I dont got many widgets, miui clock, google voice and google search, along with lookout running in the backround.
granted I cant say the same for everyone else cause I'm sure they got more running and widgets ect. I actually havent had that much of a problem.
if you guys havent yet, get the extended battery, it really makes you wonder why they didnt just put it in stock, cause the battery isnt that much bigger (in size not capacity) than the stock one.