Win XP and 7 at work, Vista and 8 at home plus iOS.
You know though if we allow Android and iOS you should probably allow for X-Box and PS3. I watch Netflix and Youtube on my PS3 as well as photos, video files, mp3s and more. The X-Box has HBO Go and while I haven't explored it yet I know it shows up on my PC's networked devices. Over the weekend, I paired up my iPhone with the PS3 youtube and was searching for videos on the phone and playing them with the PS3 on the TV. I think the future is just going to muddy the waters more with this stuff.