It's cheap (WAY cheaper than Satellite and Cable as you only pay one time, no monthly costs), You can get an amazing number of channels...many more than your cable or satellite company can provide, you can watch TV that's coming from almost any country in the world (even Cuba!), watch all the big sporting events that aren't available locally etc., and it's fun! If you're a channel surfer (as I am), you'll be in heaven.
Also, you can watch this from anywhere you have your computer or laptop and an Internet connection. So...if you're traveling you can take it with you. I have an aircard that let's me connect anywhere wirelessly, so I even watch TV in the airport or the car...anywhere really. Very nice!