I have the majority of my MBP's, MBA's & my Mac Pro, running Snow Leopard 10.6.8.
I purposely bought a new 2012 MBA just because it came with Mountain Lion, therefore I knew I'd have the best possible experience, and way to evaluate ML for my needs.
While it's not bad, as I suspected it irritates me to see the influence and tiny icons of iOS type apps etc. I abhor autosave, it is incredibly annoying. So many features that don't appeal or I don't want must be turned off. Yet not all can be.
After two frustrating years with MobileMe, it's clear that Apple doesn't get cloud services. iCloud is no better for my purposes. Therefore I won't be using that either.
So for the immediate future I'm celebrating the exemplary fast, fun, and ultra reliable performance I continue to enjoy with SL.