Bad in the sense that watching TV is usually less interesting and productive than much of anything else, but good in the sense that every once in a while, wasting time is a good way of relieving stress. If you don't watch it, you should. Well, all of them from the first 2 years at least. The Simpsons is still pretty funny after all these years. The X Files is worth watching most of the time, especially if you're interested in weird sci-fi stuff.
Friends is usually amusing.
The Practice is a decent legal drama.