My upgrades from Snow Leopard to Lion and now Mountain Lion all went without to much heartache. I am still using an Epson Stylus Pro 500 and an Epson Artisan 800. Epson had new drivers ready when I did the upgrades. The only software that didn't conform with the upgrades was Nikon Scan 4. Nikon informed me that I would have to get a third party software product that would support my Nikon Coolscan 9000 such as Silverfast. Imagine that, my software is no longer supported by the company that makes my hardware. Just as long as Nikon doesn't tell me that my camera needs a firmware upgrade but they don't do that anymore and I need to go to a third party for that firmware.