Barely nowadays, maybe 3-4 hours a week, that is actually watching TV and not just having it on whilst doing something else.
National Geographic, Discovery Channel and Animal Planet have some interesting shows and documentaries like Planet Earth, Mythbusters and Time Warp. Every now and then I'll watch an episode of a cool show on Comedy Central, like My Name Is Early or Futurama, and if there's a cool movie on I'll watch that.
But I prefer to use my TV for gaming and Blu Ray movies. Cable looks like utter crap on that thing anyway.