This is technically incorrect. Linux is indeed an operating system. Ubuntu, Red Hat, Suse, etc. are essentially GUI's that run on top of the Linux kernel. A parallel could be made to MS-DOS/Windows. MS-DOS was an operating system that ran under Windows 3.0, 95, 98, and 98SE GUI's. In Windows XP, Vista, and 7; the DOS prompt is actually a VM. These interfaces ride on an NT kernel.
I've been reasonably happy with it. Anything I can't do with Unity, I can open up a terminal and do it the old way. Also, you can get rid of Unity and put KDE or Gnome in its place if you want. [edit] I have never actually installed it, but I have a Live CD of Ultimate Edition that seems pretty nice, also. There's a "Gamers Edition" that is supposedly really good for gaming and making better use of better graphics cards. It's running on an older Linux kernel (3.0 I think), though.
Well, i attempted to generalize, because if you go ahead and lookup "windows O.S." some of the main results will bring up Windows 7 or w/e I do apologize (and i'm correcting) my affirmation.
I am not too happy with Linux but I have both Linux and windows 7 installed so I can switch over whenever I want....