Do you get your TV via cable or satellite? If yes, then you typically shouldn't have to worry about the digital TV transition. Most cable TV companies are continuing to broadcast television in an analog format over their wires even after the transition. The other alternative is that the cable TV company could provide you with a set top box (cable box) to do the tuning. Cable companies typically charge for these types of boxes and cable companies don't particularly like boxes either because they typically are not a good return on investment for them as they become obsolete quickly.

Do some of your televisions get your TV from an antenna? If you have a TV with a ATSC tuner (most HDTV's) you will not need a tuner or converter box for the Digital TV / HDTV transition. It is possible that you will need a new antenna. Unlike analog television where if you have bad reception, you get fuzzy or clouded reception, with Digital TV, when you have bad reception, you don't recieve the signal at all. Thus you might need a better antenna.