As long as you're connected to Wi-Fi the majority of the time, you should be fine with it always on. Wi-Fi uses less power than cellular. When you're not connected to Wi-Fi, that's when leaving it on will drain more battery. It'd be nice if the geofencing would auto turn it off. It's really only half implemented right now. Anyway, I'm connected to Wi-Fi most of the time and I'm seeing the same battery performance with 8.1 as before on my Icon. Maybe a little better. If you're not usually connected to Wi-Fi, you should not have it on by default.