Title pretty much says it all. Which operating systems and versions/distros do you use?
I can answer this question for all forum users. As could be predicted, the most used here is Win7 x64.
Here's the OS part of the user agent for one day of web hits to this image, which is in some thread on this forum:
Android 2.3.6; Linux; Opera Mobi/ADR-1309251116
Android; Mobile; rv:25.0
compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0
iPad; CPU OS 5_1_1 like Mac OS X
iPad; CPU OS 5_1_1 like Mac OS X
iPad; CPU OS 6_1_2 like Mac OS X
iPad; CPU OS 7_0_3 like Mac OS X
iPhone; CPU iPhone OS 7_0 like Mac OS X
iPhone; CPU iPhone OS 7_0 like Mac OS X
iPhone; CPU iPhone OS 7_0_2 like Mac OS X
iPhone; CPU iPhone OS 7_0_3 like Mac OS X
iPhone; CPU iPhone OS 7_0_3 like Mac OS X
iPhone; CPU iPhone OS 7_0_3 like Mac OS X
Linux; Android 4.1.1; HTC6435LVW Build/JRO03C
Linux; Android 4.2.2; Galaxy Nexus Build/JDQ39E
Linux; Android 4.2.2; HTC One Build/JDQ39
Linux; Android 4.3; Nexus 4 Build/JWR66Y
Linux; U; Android 4.1.1; en-ca; HTC One S Build/JRO03C
Linux; U; Android 4.2.2; de-de; Nexus 7 Build/JDQ39
Linux; U; Android 4.2.2; de-de; Nexus 7 Build/JDQ39
Linux; U; Android 4.3; en-us; Galaxy Nexus Build/JWR66Y
Macintosh; Intel Mac OS X 10.7; rv:17.0
Macintosh; Intel Mac OS X 10.8; rv:24.0
Macintosh; Intel Mac OS X 10_6_8
Macintosh; Intel Mac OS X 10_6_8
Macintosh; Intel Mac OS X 10_6_8
Macintosh; Intel Mac OS X 10_7_5
Macintosh; Intel Mac OS X 10_7_5
Macintosh; Intel Mac OS X 10_7_5
Macintosh; Intel Mac OS X 10_7_5
Macintosh; Intel Mac OS X 10_7_5
Macintosh; Intel Mac OS X 10_8_4
Macintosh; Intel Mac OS X 10_8_5
Macintosh; Intel Mac OS X 10_8_5
Macintosh; Intel Mac OS X 10_9
Macintosh; Intel Mac OS X 10_9
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Macintosh; Intel Mac OS X 10_9_0
Windows NT 5.1
Windows NT 5.1
Windows NT 5.1
Windows NT 5.1; rv:25.0
Windows NT 6.0
Windows NT 6.1
Windows NT 6.1
Windows NT 6.1
Windows NT 6.1
Windows NT 6.1
Windows NT 6.1
Windows NT 6.1; rv:25.0
Windows NT 6.1; rv:25.0
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64
Windows NT 6.1; WOW64; rv:24.0
Windows NT 6.1; WOW64; rv:24.0
Windows NT 6.1; WOW64; rv:24.0
Windows NT 6.1; WOW64; rv:24.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.1; WOW64; rv:25.0
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64
Windows NT 6.2; WOW64; rv:25.0
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64
Windows NT 6.3; WOW64; rv:25.0
Windows NT 6.3; WOW64; rv:25.0
Windows NT 6.3; WOW64; rv:25.0
X11; Linux i686
X11; Linux i686; rv:17.0
X11; Linux i686; rv:25.0
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64
X11; Linux x86_64; rv:25.0
X11; Linux x86_64; rv:25.0
X11; Linux x86_64; rv:25.0
X11; U; Linux x86_64; en-US; rv:1.9.2
X11; Ubuntu; Linux x86_64; rv:25.0
X11; Ubuntu; Linux x86_64; rv:25.0
Windows NT 6.0 = Windows Vista or SBS 2008
Windows NT 6.1 = Windows 7
Windows NT 6.2 = Windows 8
Windows NT 6.3 = Windows 8.1
Macs in second place, with Linux, iPads and iPhones, and Android also a putting in a good showing.
Yes, I know who you are (see the quote in my signature); I actually can't disable logging on my webhost. If you don't like being tracked by third-parties everywhere you go on the web, you should install
RequestPolicy.