Humor me and just try using the phone for the rest of the day with WiFi off. I did that a couple of days ago and the battery life was unbelievable. I now have wifi on most of the time and I still get ridiculously good battery life.
I'll give it a shot and report back tomorrow. Just out of curiosity, what do you consider "unbelievable" battery life? And what kind of user are you on your phone on a typical day?