Still on Snow Leopard and have no intention of upgrading, ever.
Mainly because my iMac is feeling it's age and has thermal issues (have to have the front cover off)... and I will be replacing it with a new Mac Mini.
So, basically, my next OSX "upgrade" will come with my next new Mac.
As for features... I haven't seen anything in Lion and Mountain Lion that I would want. At least the IOS app crap isn't default, like Winblows 8 Metro. And I definetly don't want my shit in the cloud... so there better be a way to avoid signing up for iCloud, as there was for my iPad 3.