I have a 2009 MBP and a 2012 MBP, both run fine on Yosemite as far as I can tell. Photo Ninja, Adobe work fine, can't advise on NX2.
RE: the icons: When I first was able to borrow the use of a Mac, I fantasized about how, when I had my own Mac, I'd change the stupid icons to ones that I thought were better. Now, I realize what a colossal waste of time that'd be.
One look at Windows, and you're grateful that they're as good as they are.