I'm having the same battery issues, before ICS I would end the day at 50-60% now it's down to 20-30%. Yes, I'm using it a little more to find out all the new features but didn't think it was that much use. Still it's a great update and I like how I can disable a lot of the bloat on a non rooted maxx.
For me, battery life took an immediate dip right after the update, but returned to normal after 3 or 4 charge cycles. It may have improved on its own, but I did try a couple of things, including fully charging it while it was powered off, and doing a system cache partition wipe like so:
Wiping the cache partition
-Power the phone off
-Press and hold the volume down, volume up and power button until the recovery screen appears.
-Use the volume down button to select "Recovery" and then press the volume up to confirm the selection.
-The phone will do a little reboot thing, display the dual core logo thing and then an Android next to a triangle with a yellow exclamation point will appear. At this point press the volume up and volume down buttons at the same time.
-If you did everything correctly you are now at the Android System Recovery Screen. To clear the cache press the volume down button until you have selected "wipe cache partition".
-Press the power button to confirm the selection and it will wipe the cache partition.
-Once the cache is cleared press the volume up button to select "Reboot System Now" and press the power button to confirm the selection. If the "Reboot System Now" is already selected then just press the power button to confirm the selection and the phone will reboot.