If I were in the market for a new TV, and Apple made TVs, I'd certainly consider them, along with whatever else was available. I might be willing to pay more for an Apple TV, if it offered additional featuress that I wanted. Apple has a track record of announcing products that don't particularly interest me, but once I learn more about them, I become intrigued, and once I finally buy them, I get hooked. The iPhone didn't interest me when it came out (I was fine with whatever basic Nokia phone my cell-phone company provided for free with contract), but once apps became available, that changed everything for me. When the iPad came out, it struck me as an expensive toy that couldn't do anything my MBP couldn't do, but after a year of friends telling me how great the iPad was, and how you had to use it to understand why, I finally caved in and bought one. Since then, I've used it every day, and I only use my MBP for heavy typing, photo processing, and music creation. So my inclination is to give Apple the benefit of the doubt, rather than proclaiming the iTV to be an "overpriced epic fail" before it's even been announced, for gawd's sake.
Having recently purchased a 1080P 2D/3D projector and 120" screen, though, I have no interest in buying a 55" TV, Apple or otherwise; however, I would be interested in a set-top box, depending on features and cost. There's been a lot of discussion in these threads about how TVs don't seem like a viable market for Apple, because people generally keep their TVs for seven or eight years. Wondering whether any research has actually been done on this, I did a web search, and found the following article, which has been posted in various places:
http://gigaom.com/video/tv-replacement-cycle/
It says that the conventional wisdom of a seven-or-eight-year upgrade cycle is no longer valid. With the new features and dropping prices on HDTVs, many people are trending toward a three-to-five-year cycle, similar to that for computers. Furthermore, many people are buying multiple TVs. They buy the latest and greatest, and move the previous primary TV to another room. I'm sure the folks at Apple have researched this, and they wouldn't be moving into the TV market if they didn't think they could succeed. Go back through the MacRumors archives and read about the rumor buzz leading up to the announcement of every new Apple product. Half the people posting predicted they'd be failures, and that Apple was doomed.