Cool! I was going to start a thread asking this very question. I just - this afternoon! - picked up a 2002 Trek 1000 to replace my FrankenFuji that I've been riding for the last three years, but the Trek has a Sora 8-speed drivetrain and I was trying to figure out how I could slowly upgrade to a 10-speed setup. Good to hear I don't really need to. As it is, I'm getting ten more gears anyway, since the Fuji is a 7-speed double and the Trek is an 8-speed triple.

So now the questions are: 1) do I even bother upgrading to 9-speed when - not if - I upgrade, and 2) if I do go to 9-speed, can I do it piecemeal, or do I have to upgrade the entire drivetrain at once?