The first few days with 8.1 it was awful, on both my Lumias (521 and Icon). I think it must've done a lot of background stuff.
Now I get very little use... I only have the 521 as a backup phone, and it's going on 4 days since last charge, sitting unused, with cellular data off but WiFi on. My Icon with normal use gets about 15 hours. At night, it only drops maybe 10% overnight with cellular data off but WiFi on.
I guess it also matters which apps you use and what you allow to run in the background. Disabling cellular data seems to help.
For some reason, it seems that IE is a battery hog, and surprisingly so is Messaging (SMS). I get the impression that the keyboard/touch functionality of the display is using a LOT of battery, at least that's how it seems to me.