My 8GB iPhone usually gives me about 4.5 hours of web browsing with no music, 3.5 hours with music (256Kb/s VBR), and 20 hours of audio playback. I've found that the standby time is absolute rubbish, seeing that I have to charge the damn thing from 70% every morning. I don't even try leaving it on for two days in a row. I have never been on a call for more than two hours, so I can't really give an estimate on that, but I will say Apple's reported 8 hours is probably wrong.