The real problem with the battery as I see it is that you can't swap it out. Not only does this mean you can't take a spare with you it also means you can't swap it out for a more powerful one.
Look at some of the more popular winmo devices, most of them have some sort of super battery for sale. Yes it increases the thickness, but hell even if you doubled the iphone's thickness it would still be thin. And honestly, while it may last a few days on light usage, it can be drained in sub 3 hours with heavy usage.
If they doubled the thickness and made all the extra battery and it lasted for 15 hours of HEAVY usage I think you'd have more people happy than upset. Just my 2 cents.
I totally agree with this, I use my phone a lot at work and home but at work I have the ability to plug it in and have it charge so the battery has been a non issue thus far. I'm going to start traveling more next week though and all of these posts have me worried that I'll be stuck with a dead phone. Has anyone tried portable battery packs. If so how do they work? I have a link to one below so you know the type of device I'm talking about.
http://www.jr.com/kensington/pe/KEG_33442/