I think what pigoo is saying there is that you need to make sure all your important apps are compatible with Mountain Lion. In most cases this is a simple matter of making sure you have the latest version. He's probably not saying (as I initially interpreted it) that he knows your apps are all going to work.
I personally recommend that before you upgrade, you make a bootable clone of your hard drive (as well as a Time Machine backup) to an external drive. That way if you find that some crucial app DOESN'T work, you can just boot from the clone drive (or restore back down to Snow Leopard) until you can update the app.
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