The biggest complaint many have about the iPod is that it lacks a replaceable battery. Personally I don't think this is an issue and I'll tell you why... toothbrushes, in particular electric toothbrushes.
I know that might sound a bit weird but it occurred to me when I was brushing my teeth that no one ever complains about the lack of ability to replace the battery in a rechargeable toothbrush, especially when they use NiCd batteries. These batteries develop a memory that would make an Alzheimer's sufferer envious if they could remember what it was that should have them envious in the firstplace. This memory is actually a bad thing when it comes to batteries because unless you drain the battery completely before charging the battery's capacity becomes less and less until it's useless.