My battery experience
First 2 days, I was on 25% screen brightness, turn off all syncing options, turned off GPS, no WiFi, turn off 4G internet when not using it. And I was running out of my battery quickly (after 2-3 hours), with light to moderate activity (browsing for 10 min, few text messages, few short phone calls, opening calendar occasionally). I noticed that the battery life plummeted markedly when I turned on the 4G and used the browser. I think the problem for me is clearly the 4G. Not sure if the phone is switching between 4G and 3G much, trying to find a signal, and losing battery because of that--- I didn't notice it doing it that much. I'm in a big city that has 4G.
Today for the first time, I used the 4G to 3G switch (phone info). I left the 3G on all day, and I don't have any issues with maintaining a 3G signal. I had the screen at 25% brightness. I had sync options on, and was syncing my e-mail accounts (work and Yahoo), and my calendar, on a once hourly basis. I was also syncing my weather every 3 hours. I had GPS turned off. Looked at my calendar a few times. Listened to 1 song. Checked a few emails. Didn't really use the browser. For the 1st time, I've gone throught the day without running out of battery! I had 40% left at 6 pm, which was great, but still a bit lower than I expected for light-moderate activity. I was going to put push mail on at that beginning of the day, but figure I'd do hourly syncing on 3G first to try that out.
Anyway, I noted that 4G isn't that much faster for 3G for basic tasks like e-mail, most web browsing, so not sure why I need it for those activities..... I will turn on 4G as needed, such as when I'm streaming a movie trailer....
My big question is, whether 40% left at 6 pm on a work day is good, with relatively light use (I tried not to use it much today). If I use the phone a bit more, it may be dead before I leave work. I'd have to have a charger at work, which I'm not crazy about doing. My main concern is running out of juice, and having an emergency and not being able to dial 911!! My friend with an i*hone has push mail on, and gets much better battery life than me. I'm thinking of returning it, but not sure, and getting the i*phone to get better battery life. I like having 4G as an option however. I really like the Android system, but not sure it offers me much over iPhone with respect to applications, except for Swype which I love. I don't really need the Widgets, especially since they were eating my battery up earlier when I used 4G. I'm coming from Windows Mobile 6, which sucks badly, so anything is an improvement. Also, I also don't like the weight, it's very heavy and wide. A massive difference from my HTC Touch Diamond (2.8" screen, ~ 4 ounces).