hehe, as i do agree that airplane mode is the best when it comes to battery conservation...however, it cripples the phone =)
Edge though at least lets you keep your device for what it is...a PHONE...
I dont get great Edge phone quality though, sometimes sounds just awful, and disconnects if i go somewhere like a supermarket or home depot. 3G however lets me talk pretty much everywhere....even the only tunnel that we have in my county =) Edge will drop off in the middle of the tunnel or in a elevator.