Just a few notes from personal experience. If you mess at all with the WiFi power settings, your battery life will really, really suck. Also, beware desktop widgets that display info that gets updated regularly. I was warned at the Summit by people in the know that the Facebook widget isn't very power-optimised. If you need better battery life, turn off e-mail checking, too. I've heard reports from hard-core users that it can really help your battery life. Taking a lot of photos really seems to hammer the battery. Best thing to have is that "load-applet" mentioned above and watch the left indicator. If it stays at four squares, with the top one flashing red, for any length of time, your battery is headed for a premature demise. I notice that occasionally (seems it might be related to XChat? Not sure), some mysterious process called hildon-xinput-sounds hammers my CPU and I have to kill it or suffer a quick battery death.