One of my many problems with the iPod was the fact that it had no removable battery. Another was the price.
Once I found a 40GB iPod at a much-reduced price, I jumped on it. As far as I was concerned, this was like getting an external harddrive with an internal power source... and it just happened to play music, too.
So, that got me over my removable battery issue with the iPod.
The iPhone, though, lacks that huge capacity (although I find it impressive for what it is) but gains the burden of being a primary communication device.
Despite my issue with it, I think it's a very impressive device. That said, some of those issues are real deal-breakers. For me, lacking a removable battery is waaaaay up there.
I'm usually fine with a single battery, but when I travel, I *always* regret it if I leave the extra battery at home. There's always some reason I don't get to charge the phone as long or have to use it much more.
And, as others have said, if my battery ever croaks, I don't want to have to take it to, go to, or pay for an Apple store for what should be a simple replacement.
Besides, there are no Apple stores where I live. None.
C'mon, Apple. Some folks use their mobile phone as their ONLY phone! Most consumers might not care that it lacks a removable battery, but I do.