You can get a $40.00 coupon from the government toward a converter box to make your existing TV work. You can also buy cheap TV's that have ATSC tuners but only 480i display. Personally, if I was going to spend the money and pick up over the air signals I'd go ahead and buy a HDTV. The over the air transmission has some of the best HD picture quality second only to Blu ray.

ATSC will allow you to pick up your locals you receive now and if available your locals may offer some additional stations. For instance, here in StL the NBC affiliate has there regular broadcast in HD on 5.1 and a 24 hour weather channel on 5.2. Our PBS station has really gotten into the deal offerin 9.1 - 9.4. One is the regular programming in HD, one is 24 hour PBS kids and I'm not sure the theme of the other two. If other locals follow this trend, free digital over the air signals is going to be a very good thing for the consumer. I assume if you use the converter you will receive all the same stuff but converted to analog 480i to play on your existing TV.