For most people the iPhone is a daily charger. For me it's not a big deal because I use it as an alarm clock, so when I sleep, it charges. Having said that I've only once had it go into the red during a days use, and I use it as an iPod, lots of texting, facebook, general browsing and the odd game.
I've come to the conclusion that as a computing device, it's very efficient, I often sit with the kids playing CPU intensive stuff like Aqua Forest for hours, and the battery hardly takes a hit. Wifi does make a dent though, and 3G absolutely canes it. To be expected really.
I have ordered a USB charger which powers from AA batteries, which I'll drop in my rucksack when I'm out and about. Should help with emergencies, not that I've ever had one!