Yesterday after my first full charge (a new iPhone 4), it lasted about 7 hours or slightly more of usage with standby time of about 20+ hours, left about 4% battery when I plugged in to charge.

I think it should be fine right considering I have some notifications going on as well like notifications from Echofon, mails (set to fetch every 15 mins for 5 accounts) plus some usage of listening songs for a while, on the phone for about 30-45 minutes and 3G was on all the time (with occasional WiFi connection for downloads).