I currently own an early 2008 iMac (2.8Ghz C2D, 4GB RAM) running ML. It's not that I'm unhappy with ML, but I miss the 'snappiness' I had with SL. I just don't feel that my iMac has the necessary horsepower for ML. I'm therefore considering downgrading back to SL. However, I'm also interested in buying an Apple TV3. What would I be missing out on if I didn't have ML anymore, apart from the iCloud stuff and considering I can still run the latest version of iTunes on SL ?