<< What are the differences between the SP100 and the SP90 that justify paying extra for the SP100? I see the SP100 has a remote that the SP90 doesn't, but thats hardly worth the $50 price difference. >>
AC Adapter, case, better headphones, flashable firmware, and a backlit screen. I think that's it. I really didn't need any of that (except maybe the backlit screen), so I got the SP90 and I'm thrilled with it. One of the best purchases I made this year.