Until the other day, when I discovered that the Slingbox player requires Snow Leopard or Lion. Ugh. But, I remembered reading something about doing a clean install vs. an upgrade, so I did some Googling and found instructions on how to do a clean install, even though that is not listed as an option when the upgrade disk is run.
I did a Time Machine backup, fired up the Snow Leopard upgrade disk, and followed the directions to do a clean install. The OS installed perfectly and then asked if I had a Time Machine backup. I plugged in the external drive, and all my apps and data were reinstalled. System came back up, looking just like it did before.
And, the touchpad? Works perfectly!
Lesson learned: when it comes to OS upgrades, a Mac can behave just like a Windows box. I never! do Windows upgrades from one major version to another; I always wipe the drive and do a fresh install. Looks like that needs to be the rule with Macs as well.