I used to use PP2014 on a new retina IMAC (and a 27 inch iMac before that) and it worked fine. If they've fixed the issue with reality and el capitan, then you should have no trouble with anything that I used. I have switched to DAZ Studio, and wish that I had an nVidia card, but otherwise, I'm fairly happy. The only "Add-ons" that I'm aware of that don't work are some really old python scripts that use TKinter for the interface which apparently is missing on the version of Python that comes on the mac for some reason. But, those are from years ago.

If you use Mac at work, then you'll be much happier not having to switch back and forth from mac to windows. I was a huge window's nerd before I switched (built my own machine, etc), and now I'm completely at a loss when I sit down to try and help folks with their windows machines. Nothing is familiar to me anymore...but, then again, it's probably been over 10 years since I really used one of those machines.

If you are getting an iMac, I recommend getting a wired keyboard if you don't plan to need it far away. My previous imac had a wireless keyboard and it went through batteries like crazy. The wired mouse is horrible, though, so get the wireless one. It's really nice. Also, keep your machine in good shape and you can get a really good trade-in value many years later. With discounts (got it during the thanksgiving sale season last year, so they were offering some extra incentives for trade-ins), I think I got over 1000 off of the price of the new one, and the machine I traded in was 3 or 4 years old.