One of the advantages of the computer rebuild is that it gives you a chance to fix (by every tech support desk’s favorite method, a fresh system) little niggling problems. E.g., that IHateSpam came up with a (non-critical, but still annoying) “I crashed on start-up, do you want to tell Micro$oft?” error every time I booted my machine. Or that my old Adobe install was messed up so that when I would open a PDF, it would inevitably run a “I’m finishing configuring Adobe Acrobat” dialog.
It’s also an opportunity to not install stuff you’ve changed your mind about. Like, for example, Google Desktop.