I have a 2015 top-spec retina MBP, plus a 2013 MacBook Air and 2013 and 2015 iMac 27 (I'm a video editor). The 2015 MBP is very good, and if it's your only computer it's better than a MacBook Air. It has good battery life and the retina screen is great. The force touch trackpad is a nice improvement. That said, if you don't need the 15 inch screen a top-spec MacBook Air is very nice and a lot thinner and lighter. If you don't need portability a 21.5 or 27-inch iMac is probably a better fit.
But if you just want to start with Apple on the 15" 2015 MBP, you won't be disappointed. It is very refined -- every little detail is "just so".
OS X is very nice but try to have balanced expectations; it has some bugs like all other software. It does have a few major advantages such as updates are much faster and less intrusive than Windows, also the entire OS can be re-installed while retaining all your apps (no registry).