my iPhone rarely runs down. The 1.0.1 software fixed my problem with the car audio/charger adaptor, so now I plug it into the thing in the car to listen to podcasts while I'm driving, so that tops up the phone whenever I drive in or home. When I'm at my desk, at least once a day I plug it into the computer to sync my bookmarks, contacts and get any new music or podcasts into it, and if I leave it plugged in there more than a few minutes it tops up the battery there. And on my bedside table I have the charger it came with plugged in and plug it in when I go to bed. The only times it's run down was when I was testing to see how long the battery would last. Do other people really just not plug their phones into anything ever? I didn't when I was just using a phone, but since this is an iPod too I have to plug it into the computer constantly to get new content to listen to anyway.
What part of the more difficult to replace battery bothers you most? Are you afraid that you'll run out of power half way through the day? Or are you afraid that you'll forget to plug it in for a few days and it will run down? I have a couple of battery packs for the iPod which work just fine with the iPhone too. I have one in the glove compartment of the car and another in my bug out bag so that I can charge it from any old 1.5v to 9v battery source I can find in the case of an emergency. I do know some people that use a phone so much during the day that they actually change batteries over lunch. But they are not numerous enough to warrant a change in form factor design.
Apple has had a ton of success with the iPods non-user removable back. I dont expect them to change the form factor of the iPhone either. In a couple years I'll spend an hour with my iPhone and solder in a new battery. The 3rd party kits are already available. I expect around the same time a bunch of my friends will start asking me to do theirs as well, like they now do for their iPods
If I only have to change a battery once every 2 years or so then I dont mind it being a little more difficult. I'd gladly waste an hour in 2 years so as not to have a flimsy case that bends more easily to break the lovely screen. The vast majority of cellphone batteries are never changed at all. They are snapped in at the store and then end up in the trash without having ever been changed at all. Regardless of the price of the phone they are in. So why take something as strong as the iPhone case and make it easier to break in my pocket?
I never got upset at the iPods monolithic case, and I can't get upset at the iPhones either. If you ever change the battery it will be once in 4 years. I think you can afford the extra time once in 4 years if they phone actually lasts you that long without falling apart.