Here's the list of supported Macs for the latest El Capitan Beta which goes back to some 2007 models: https://developer.apple.com/library/prerelease/mac/releasenotes/General/rn-osx-10.11/index.html#//apple_ref/doc/uid/TP40016209
As for osx86, I'm running the latest El Capitan Beta just fine on my Main PC (2013ish hardware) and my old Dell Latitude E6420 (2011) without issues - the selected hardware is fully supported. If you want to have OS X run fine on your PC then pay attention to using hardware within the range of what has support, either from Apple or third parties, and you'd be able to run the OS without difficulties.
As someone who prefers almost any other OS other than Windows for my main, I still have problems believing that AAA gaming developers will make the big move to support an OS and framework that only covers a minuscule percentage of users.
I used to really be into running games under wine for Linux and OS X (osx86 *cough*), to the point where I would apply patches and do custom wine builds to get my favorite games running. I eventually just let go of it after 8 years and decided to always keep a Windows install ready for games and nothing else. That's probably why I haven't had much interest in SteamOS. It's a wonderful idea and I support it, but you need to win over the big players. The big players will most likely find SteamOS support to be financial waste. I'm glad that the amount of Linux games on Steam continues to rise, but like TFA says, it's just not worth the time and effort to optimize for Linux and in many cases not even try at all. There are many Windows applications that use a cross-platform framework that has wonderful support in X11, but why won't the company release a Linux or *nix version? Time, money, and less profits based on the amount of active desktop Linux users.
As the way things are going, SteamOS will be a great platform for indie games, that's for sure. But Ubisoft? Rockstar? EA? Activision Blizzard? I don't see that happening in the foreseeable future.
Perhaps I'm just getting old or something, but I've actually started to move closer to consoles, even with my nice PC setup that was the latest and greatest in 2013 which I keep around. The interest with indie game developers porting their PC games to PS4 makes me feel I made the right choice with getting one over an xbone. I wish the wave of Linux gamers receive the support they need to defeat this obstacle, but with its small percentage and the fact that it comes down to money and manpower to port and optimize games, it will unfortunately take some time for this to become a reality. If it happens, expect me to be there and ready to make the move from Windows when it comes to gaming.
Though the source code has supposedly been released under GPLv2, according to their website. Confusing.
"Of course power tools and alcohol don't mix. Everyone knows power tools aren't soluble in alcohol..." -- Crazy Nigel