As you can tell there are a variety of results out there. I'm on Sapphire and find I take the phone off the charger at 5am, and right now, at 8pm it says 20% left on the battery. On some other roms I definitely had to plug in during the day or be out of juice. I've heard good battery life on a couple of roms but not leaving GPS and WIFI on all day when not needing those things has to help as well as good overclocking speed management.
Switching to other roms is easy. Go find their announcement install page and there should be screenshots and instructions. If instructions aren't there I'd ask for them before proceeding.
Always back up what you have now before flashing another rom or kernel.