Slow Shutdown is not universal. I don't have it on my rMBP. Either that or people's definition of slow isn't the same as mine. It takes at most 15 sec for mine to shut down and mostly it's around 5 seconds. That's not slow at all for me.
Universal was a bad choice of words. I should have used "widely reported." I almost never shut down any of the computers I use, so I couldn't even say which, if any, of my computers are slow to shut down.