Information Week has posted an article that indicates many people are having problems upgrading their Macs to Snow Leopard. It looks like Apple is trying to pull a Vista on it’s user base: release an update that isn’t ready and is going to make more headaches for users than solve problems. At the bottom of this article is a link to “100 Incompatible Mac Apps” for Snow Leopard (here is a link to the Wiki with the list of apps and their compatibility). I’m not sure how that helps your existing user-base and adoption of a new version of an OS, but Apple hasn’t always been the best when it comes to backwards compatibility.
If you run a Mac, my suggestion would be to wait until Apple releases an updated version of Snow Leopard.
If you need to upgrade to Snow Leopard, first make sure that any of the apps that you need to run are supported. Then run update and make sure that your current version is up to date. Then make a complete disk image backup of your disk incase the upgrade destroys your install.