I've give Apple props for the iPhone to a certain extent.  However, just like their PC's, any type of maintenance is to be done only through them (Apple/ATT).  I mean come on, lets design a phone heavily dependent on a battery and then make it not easily replaced by the average consumer?  The first gen was soldered to the circuit board while the newest is a pressure contact.  Unless you're good with electronics and want to void any type of warranty you had, you're not going to be able to replace it.  A buddy of mine at work just picked a 3GS and as much as he plays with it he's charging it at least twice a day.