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I was just looking at the Steam Hardware & Software Survey, and it shows 95.35% Windows usage, 3.42% Mac usage and 1.16% Linux usage. Naturally this is viewed through the filter of "people who use Steam". For those of you who see actual real sales of your games outside of Steam, do you observe similar distribution figures? Or is Steam more heavily used (proportionally) by Windows users, thus causing slanted numbers?
That seems pretty similar to the usage share of operating systems as a whole given by a number of sources in the Wikipedia page on the topic, so I would assume it's fairly reasonable.
According to this page the numbers from Humble Bundle sales (looking at the combined purchases rather than payments) also seems fairly similar with only a slight increase in the numbers for both MacOS (8.99%) and Linux (5.19%).
I'd be interested to know how those numbers compare to the percentages of games that actually support each platform; many games simply don't support one or both of Mac/Linux, which I expect would tend to naturally skew overall sales in favour of Windows. Obviously this doesn't apply to the majority of Humble Bundle sales, as most of them touted cross-platform availability of the games as a major feature.
cheaper: linux or pirate win, win, mac
easier to use: win, mac, linux
Doesnt that pretty much explains everything?
Plus, is commom knowledge that windows is the gamer platform for home computers. One does not by a mac "to play games".
Partly because game players tend to favor it. But also partly because of virtualization.
Naturally this is viewed through the filter of "people who use Steam". For those of you who see actual real sales of your games outside of Steam, do you observe similar distribution figures?
Lots of people who use a Mac and play games will have a virtual install of Windows. Lots of people on Linux will use a VirtualBox installation (with the DirectX extensions) or WINE (with WineD3D). Sometimes it works great, sometimes not so much. Lots of games work just fine inside it.
A side effect of that kind of portability is that the target becomes that much more valuable. More people show up as using Windows since they are inside a Windows virtual machine.
The effect happens in other places, too. When a group wants to have their file formats or their systems become popular one of the best things they can do to help themselves is to write importers/exporters for their competitors. Make it easy for other groups to move in to your product, and reduce the fears that they will be locked in to your minority-share product.
I think linux numbers are always a little lower for a few reasons. For example, we tend to dual-boot (or as frob mentioned, use WINE or a VM), and thus, often get counted as Windows sales, if the Steam survey comes up when we're in windows. Additionally, releases for linux are often considerably after the windows version, and often, many will opt to just buy the Windows version than wait for the linux release. We're still a small demographic, to be sure, but I don't think quite as small as the survey shows.
I think the linux community is starting to hold out and buy things when they're officially released for linux, as it's becoming more commonplace (borderlands the pre-sequel and civ5 come to mind as day one releases, and countless indie games), so I think as that becomes more common the numbers will rise. And, of course the release of Steam Machines is expected to boost things quite a bit, but we'll see.
It's been said often, I'm sure, but I think linux is finally coming into its own and may soon be a real competitor on the OS front, despite the current small numbers. I've personally wiped my windows drive years ago, as with the exception of a handful of games, my linux drives can suit any need I have (not to mention the pretty large benefits of a linux system).
easier to use: win, mac, linux
Anyhow, my two cents, user experience may vary and all that 
edit* I also completely mean the next civ game, not civ5, which came out years afterwards (thanks to aspyr, those guys are great :)).
For example, we tend to dual-boot (or as frob mentioned, use WINE or a VM), and thus, often get counted as Windows sales, if the Steam survey comes up when we're in windows.
Me too but I play mostly on Ubuntu Metro Last Light or Wolfenstein in Wine. Hence I probably get counted 50% Win and 50% Lin? After Project Cars I might go to 75% Linux. 
There's the "Unity stats" data as well:
Irrelevant as not cross platform and this thread being about steamos.
