Windows. I've been using it for years now and I'm very comfortable with it. I'm using Windows 7 and I like it much better than Windows 8.
Me too. I'm not a fan of 7 but it's much closer to their older versions. I think they have realized their mistake and it's why they're bringing back the start button for their next version.
I currently use Windows 7 and the computer frequently lags or freezes. Although it is very possible that this is an issue with my computer's hardware as I have everything updated properly.
I really did like Windows 7. It was simple, more friendly than Vista and it had a simple, clean layout. There wasn't anything fancy about it but it didn't matter. It was a good operating system. I had less that friendly impressions of Windows 8, which really screwed me up considering that I was a big PC gamer and that it's new Start layout was really weird and belonged to a tablet layout rather than an actual computer OS. I got used to it eventually, but still, it was quite odd.
I prefer it a lot more than 8 but mostly only for the ease of use since I'm much more used to that layout and I'm too lazy to train myself for a new one. I didn't like the design of it that much though.
Windows 10 definitely, really smooth and a worthy upgrade from Windows 8. The OSX isn't that bad, I love the interface but it seems kind of sluggish for me.