I have Snow leopard, which is really fast for me. So quick question - is mountain lion faster? Internet wise even? If not I'm not interested in all the other fancy apps. Just the speed is what I'm curious about!
Sort of depends on what machine you have. My 2008 iMac runs ML just fine, and I'd say there's a bit of a speed difference. Honestly, ML is probably the first OS X upgrade where I've noticed nearly nothing different (from Lion that is).
i have SL on my early 2011 MBP and wondering the same thing.. I've upgraded the Ram and HD so that maybe something to look into as well if your worried about speed..
Remember that eventually we'll have to upgrade as SL won't receive any more updates in the future...