Then I tried wiping the system cache partition and restarting the phone. Once I did this, battery consumption returned to what it was before the update
I tried this using these directions for my AT&T Samsung Galaxy S II :
1. Turn off the device.
2. Press and hold both the Volume up and Volume down keys at the same time.
3. Press the Power key only until the phone vibrates once, then release only the power key. Note: my phone did not vibrate, so I released only the power key when I saw "Samsung Galaxy S II" on the screen.
4. Continue to hold the Volume up and Volume down keys until the Android System Recovery screen appears.
5. Press the Volume down key to highlight Wipe Cache Partition.
6. Press the Power (or Home) key to select.
7. Make sure Reboot System Now is highlighted and press the Power (or Home) key to reboot.
I only had to replace one widget. When checking my battery under settings, I have 80% after 4.5 hours, the Android OS is @ 9% (down from 36%), and the Android System is @ 6% (down from 15 +%). My screen is using 75% of my battery, which is what I'd expect for how I have it set up.
I really didn't have any complaints after the ICS upgrade (like ICS better than GB) , but certainly haven't noticed any glitches since trying this.