I used wifi all day at work the past weeks without much problems, but I can understand your frustration if it suddenly eats up a lot of power. After 7 hours idling today my phone is at 81% battery now, but I have only been on the phone for like 20 minutes earlier today so "Android OS" and "Voice calls" have about 25 minutes of cpu usage each, while maps has 15% today for some reason.

My phone runs stock samsung android since I just got it:

Android 2.3.3 GINGERBREAD.XWKE2 Linux Kernel 2.6.35.7