My battery life has been really iconsistent since I started using Exchange push. Most days, I leave the house with a fully-charged battery and by the time I get home 10 hours later, the battery is still over 50%. But some days, I'll be at 10 or 20% by some time in the afternoon. (Today it was 20% at 2:30 p.m., when I unplugged the phone from its charger at 8:30 a.m.) There are not unusual volumes of e-mail being pushed on the days when I have reduced battery life, and I'm not using the phone in any unusual way on those days. I just can't figure it out. (And I'm using Edge during the day, with GPS turned off.)
It's very annoying -- even more so since I'm supposed to be testing the iPhone for work purposes for my firm. If I can't find the solution to this, I'm not sure I'll be able to recommend its adoption on a firm-wide basis. (Our managing partner has expressed interest in letting people choose between the iPhone and our current Blackberries, provided no major obstacles pop up in the month or so I'll be using my iPhone.)