One question that doesn't seem to have been asked much is "who actually wants to watch TV on their computer?" This seems like it's going to be a fairly small subset of the total number of computer users, and this should be taken into account when making this kind of decision.
Desktop users are unlikely to watch TV on their computers. The average desktop computer has a smaller (although higher-resolution) screen than the owner's TV. It often has worse sound, and generally makes too much noise to provide an enjoyable viewing experience. The exception to this is desktop computer owners who have broadband Internet connections but not TVs. I suspect that most of the people in this market are students. From wandering around campus, it seems that Apple has a much larger proportion of the market share than in the real world, and Linux does very well amongst science and engineering students.
Discounting the desktop, laptop users seem like a larger potential market. Laptop sales have now passed desktop sales, so most computer users will be laptop users quite soon (I've been desktop free for about four years, and never want to go back to using a computer that doesn't let me work outside in a deck chair).
In May, almost 15% of all laptops sold were Macs. Assuming that some fraction of those that weren't were going to run Linux, *BSD, Solaris, or something more esoteric, this means that only around 80% of laptops sold were going on to run Windows as their primary operating system. While 80% is a lot, it's still a long way from 100%.
While watching on a laptop is attractive for laptop owners, since they can do it in places where they usually don't cart their TV, laptop owners are still only a comparatively small part of the population. When we get away from traditional computers, things get even more interesting.