i know mine one may be an "out of the line" opinion, but for me, onecosmic 3.1 is best ics rom out there. It has some bugs:
- can't install chrome from the market (but it works installing it from the apk)
- .apk bluetooth transfer are not allowed (just change the extension in .jpg and change it back once is on the phone)
- other minor, not important to me, bugs.
But the battery life... well, this is unrivaled under that point of view, and since the battery of the modern smartphones just sucks...