I'm sitting here looking at my phone after reading about your HORRIBLE battery life.
I currently have the following usage and standby times:
Usage: 6 hours, 56 minutes
Standby: 22 Hours, 41 minutes
This has been on ONE full charge.
Also, i still had about 20% battery life left when I plugged it in a few minutes ago.
If I were you, i'd take it back and swap it out. The guy from the apple store that you talked to, is a complete idiot. Just know that sometimes it's hardest for an idiot to admit when he's an idiot, even if the rest of the world agrees that he is a total idiot. =)
Talk to someone else, arrange to talk with a genius or manager. I've talked to a handful of people from the apple stores and out of about 10 different people over the course of the last 2-3 weeks, i'd say only about 2 or 3 of them had any sort of common sense.
In fact, let me tell you a quick story. I was standing in line with my friend to get our iphones when we had a funny encounter.. or not so funny encounter. To start off, I wanted to get my girlfriend an iphone3g 16gb white, and get myself a black one. My friend wanted one as well, so we tried everywhere but they were sold out. So, we drove 2 hours to king of prussia mall in pennsylvania to get one. We stood in line for about 4 or 5 hours before some fat gay dude came over to us and asked if we could go through the pre-approval process. We agreed, but before he even tried, he asked us some questions.
Some fo the questions included, "Have you ever had a discount rate code on your at&t account, and does your billing zipcode match the zipcode of area code of your phone number". My friends zip code didnt match, and I did have a discount on the account. However, before we even got to the mall we called At&t and had them remove the discount because I already knew about their problems with that. The gay fat dude then decided he would tell us to get out of line and go home or do something else because he couldnt sell us a phone. Those were his exact words. It took a few minutes of arguing before finally i told him I was going to punch him in his mouth if he didnt get the hell away from me. He walked away, and another apple guy came over and asked what the problem was. I told him, "im going to punch your fat buddy in the mouth if you can't at least TRY to process our orders". I then told him that we had waited in line for 5 hours to hear this crap, and that we took care of everything before we got to the store. Apparently apple claims it takes up to 24 hours to update their system to be able to process an order after you've made these kinds of changes....well, we found out that it doesn't. The dude processed our orders for pre-approval and both of them went through fine.
This just goes to show you, that there are tons of morons in the world....
Oh, and we stood in line for a total of 7 hours before getting our iphone3g, with about another hour with activation of 3 phones plus buying accessories.