Cable: the People's Choice
About 80 percent of Americans subscribe to a cable company for their TV service, and for most of them there's a simple and affordable upgrade path to HD programming.
All the major U.S. cable companies offer some high-def programming, and service is spreading rapidly to cover even the remoter service areas. They typically offer HD versions of the premium channels HBO and Showtime, as well as some mix of HD programming from channels including Discovery HD Theater, ESPN HD, HDNet, HDNet Movies, TNT in HD, and Universal HD. You may also get access to INHD and INHD2, two stations owned by a consortium of cable companies and offering a broad mix of HD programming.
It is also becoming increasingly common for cable companies to offer their subscribers access to the local HD broadcast stations, so you won't have to switch between cable and antenna reception to pull in the local network affiliates. There are also "national" network stations that may be available in HD. Depending on where you live and who your provider is, you may be able to pull in HD broadcasts from CBS, NBC, ABC, Fox, UPN or WB stations outside you area - but it's all governed by some complicated legal rules, so you'll have to check with your provider.
For most cable subscribers, the move to HD requires swapping out cable boxes - though some HDTVs now come with an integrated cable tuner and a cableCARD slot. If, like most people, you opt for a new set-top box from the cable company, it will probably rent for a few dollars more than your old one. See if you can get a model with a built in digital video recorder (DVR) - for most people it's a convenience that's well worth it. You'll also need to purchase an HD programming tier, typically in the $10-12 per month range. If you want HBO or Showtime in HD, it's usually included with the regular versions of those channels, rather than as part of the HD package.
If you bought an integrated, "cable-ready" HDTV model, you may be able to ditch the set-top box. If your cable company supports it, you can rent an inexpensive cableCARD to break out the encrypted signals, and plug it right into your TV set. You'll lose access to certain features like movies on demand, but some companies let you order these over the telephone - check before you decide.