I recently turned my 3G off after the guy at my local MacMan store advised me to do so. (no 3G here). Before that the best battery life I noticed was 8 hours usage with over 23 hours of standby, with just 2% left. I have push every hour with 75-80% brightness on. No Bluetooth.
Typically I am getting 6.5-7 hours usage with 15ish% left.
Amazing battery life in my opinion. Much better than my 3GS..
Blonde Buddhist