I've found that the worst thing I can do for battery life is constantly moving in and out of wifi range. If I stay on GSM, battery life is pretty decent. If I mostly stay on WiFi, it's even better. This is without turning either of the radios off entirely.

When I was working in a warehouse that only had wifi coverage to about half of the place last week, I'd be switching back and forth 20 times a day, if not more. I'd get about 20 hours out of it, with pretty light usage. It was pretty much dead by the time I got back to my hotel room with only 20 or 30 minutes of talking and 10 minutes of web browsing and 10 minutes of IMing.

When I got back home, where I'm on WiFi almost all day, I left it off the charger for over 30 hours before it started complaining of low battery, but that was also with light usage. Maybe an hour of calling, a bit of emailing, a few text messages, and a bit of IMing. I can usually get 16-20 hours out of it with more normal usage when I'm on WiFi all day.

I only have the calendar and several contact widgets on the home screen I normally leave active.