MeanROM ICS works great but for me at least, it's is a total battery KILLER. While the standby time is fine, if I'm actually using the phone l get AT MOST 3 hours of battery life... and if I'm in an area with marginal signal I might as well short the battery terminals together for all the battery life I get. (No tweaks, themes, or other funky stuff installed.) On a Gingerbread ROM (I'm using CleanROM, haven't tried MeanROM GB) with exactly the same settings and apps installed I get AT LEAST double the battery life, usually much more than that.
I don't know if the terrible battery life is endemic to ICS or not (couldn't get CleanROM ICS to work) but my advice would be that unless you have a lot of time available to try this and that and see what works for you, stay with GB until an official ICS release comes out. In my personal experience, the extra features of ICS haven't been worth the trouble - though of course others may get better mileage.