Not sure if it helps, but I've been running CM9 for the past month on my i777, and battery life has been leaps and bounds better than when I ran 2.3.6. I can actually go a couple days with light usage without charging my phone, with Wi-Fi on all day. I'm loving it, I don't even think I'm going to flash to AT&T's ICS update, provided it ever even comes out. It's a little ridiculous that AT&T has taken so long to push a new update to fix the Wi-Fi battery drain issues, ICS or not.
Edit: @Wing2012, no, it's not necessary to do a full wipe when installing new CM9 nightlies provided you're already running CM9. If you're flashing from another rom and/or stock, then yes, a full wipe is necessary. If you download RomManager Premium, you can automatically check for updates, download, and it'll give you the option upon trying to install it to full wipe, cache + data wipe, or dalvik cache wipe. I just wipe dalvik and install, no issues.