Battery arguement...
OK, so the size increase arguement probably holds true, no one wants to carry a big brick of a phone around with them. And I truely do appreciate the form factor of my iPhone vs my previous phones the Treo 650 and 700.
But I'm not so convinced on the battery life aspect. In my daily life, and I'm sure countless others as well, we are near power sources all day long.
Home, office, car, plane, airport, etc.
Yes you'd have to take a charger with you, but in these places a professional would have a laptop or other bag with them to store the charger. Or in the case of the car you'd just have it left in the car, plugged in.
Personally, I have at least 4 chargers for my iPhone.
All in all, I'd rather have 3g and have a shortened batterylife. But I want the form factor as well, so we'll have to wait the "year" before the next iPhone with 3g. That should really be the killer phone as this version of the iPhone is killer-1.