The biggest drawback to digital TV right now is the price. A digital TV set can cost anywhere from $1,500 to $3,000. The price will fall in the future as more and more stations convert to digital broadcasting. You can also buy a converter box (like the old cable boxes) that goes on top of your current TV. It will allow you to see the programs on WMC-HD, but they will not appear in the new digital format because an analog TV can't show them. There are also digital TV cards you can buy for your home computer that will let you see the new digital signal on your computer screen.
You'll also need a rooftop (or some other type of outdoor) antenna if you don't have one already. It doesn't take a special digital antenna to receive the signal, any standard UHF/VHF model will work as long as it receives channels up to 83 (remember, WMC-HD is channel 52). The neat thing is that signals will be crisp and clear... there are no ghosts, static, or poor color on digital TV. You're either seeing the signal or you're not.