For me, battery life on 8.0 was ok, but in 8.1 Dev Preview, launching *any* GPS app (Here Drive, Waze, Inrix Traffic, whatever) sends the battery spiraling down the plughole! Not just when using a GPS app, but after I exit a GPS app the battery keeps draining, almost as if the GPS was "stuck" on. The phone also gets hot in the usual spot (upper right corner.) Battery drain returns to normal if I reboot, at least until I launch a GPS app again, then the rapid drain starts all over again.
The battery drains so quickly using GPS, my car charger can't keep up- it will lose about 10%-15% an hour, even while charging. (If not charging while using the GPS, it loses about 1% a MINUTE!)
I really hope this is fixed with Cyan, otherwise I might go back to my trusty Lumia 810...