This is my favorite iPhone websites-
http://weblogs.redeyechicago.com/iphoneblog/
It contains a crapload of links as well.
Scroll down a bit on the first page (at posting here 9/16/08) and there is an interesting post on battery life.
For me (1st gen iPhone) it's not what I would call great. From the reading I have done, the 3G version "can" have similar issues.
I charge my 1st gen at least every other day. My "average daily" use is less than 30 minutes of talk time, email on auto-retrieve hourly, 0-30 minutes of gaming (Apple's Hold Em' poker rocks), 0-30 minutes of iPod, retrieval of 0-5 webpages and links, weather info 0 to a few radar views.
Like any DC powered device it's all about usage. If the (unplugged) iPhone is used on WiFi/Bluetooth/3G it's going to burn more power. Some games, obviously the more processing intense ones, REALLY chew through the juice.
iPod playback doesn't seem to hit the phone really hard, but it's of course going to be a greater hit than standby mode.
If you have the phone setup to "fetch" email it will burn more than manual retrieval.
So it all depends on how YOU use the phone. From your brief note, I would say you should buy a car charger before you leave the store LOL.
I believe the camera is unchanged (hardware) from the first gen, could be wrong. No video with an unhacked phone, again could be wrong, there are SO many apps on the iTunes app store now that I could have missed and again be wrong.
Overall it's a great device, but there are some gotcha's and battery life COULD be one of them depending on usage. Texting is text only (odd statement when seen in text), but there are some workarounds (sort of) for that.