If you're a Mac user, you go through this every time a new version of OS X comes out -- will all my apps work if I upgrade?
Many users will hesitate before upgrading on day 1 because sometimes developers (though they've had months to get their products ready for the new OS) haven't updated their software yet.
The folks over at Roaring Apps have put together a massive database for you, that will allow you to see if your favorite app will play nice with the new OS.