By default wifi turns off when the screen is off AND it uses less power than 3G so you want to use it when you can. GPS only comes on when an app/widget uses it (EXCEPT FOR THIS POSSIBLE DROID X BUG). Bluetooth doesn't use much juice either. I say try leaving them on and save yourself the headache. At least try it out.
Read my findings a few posts back about the increase in battery life after I toggled GPS off. It's the only change I made in the past couple of days and I'm at almost 40 hours now off the charger with the battery still showing 30% left. Turning GPS off when not using it definitely makes a difference...and I've had Bluetooth enabled that whole time as well.