Operating systemwise? An unbelievably vast software ecosystem and a highly performant, user friendly, highly hardware tolerant, flexible OS. There are things I like to do that are either impossible or such a giant PIA on my rMBP that I just don't do them. Coming from Windows-land, the software ecosystem on Macs, especially the kind of hobbyist software I like to monkey around with, feels like a barren wasteland comparatively.
Don't get me wrong, I love my rMBP, and I get my work done on it well enough, it's the best portable virtualization hardware I've ever owned and the second Apple laptop I've owned. But I've also realized that I spend 95% of my time on it either SSH'd into something else, in a browser or using software that's also available on Windows (and often works better, like Office of Chrome). I can do those things with hardware that's 1/5th the cost and have it be almost exactly as performant for those use-cases.
For my next laptop, if I can find a high quality portable Windows laptop with good virtualization characteristics I'd be 50/50 on not buying another Apple product because of the things I have to set aside due to the spare software ecosystem. There's also enough day-to-day irritants and workarounds with the hardware and especially OS X (and especially the stinking pile of garbage that is Finder) that I find I spend most of my time trying to avoid the OS. For portability and form factor, a Surface Pro 2 is definitely something I'm considering as a next portable.
It seems these days, Apples get used in software development and server admin functions or among liberal arts students. And for the typical users (not the HN crowd) justifying an expensive price tag for marginally better portability for something that gets used mostly as a glorified web browsing terminal and Word/Excel computer is not a smart purchase decision for most consumers.