I did some experimenting with portable TV's with the digital tuners and as far as I can see, DTV sucks big time when you're moving. On an analog TV, a momentary glitch in the signal just meant a pop or a hiss in the audio or a jump or a little snow in the picture but digital sets either stutter and pixelate or freeze up entirely until the tuner sorts it all out again. Most of the stations in this area (maybe all of them?) went to lower power output and a good antenna is a "must have" item. I finally found one that works fairly well at a truck stop. It's designed to clamp on to a mirror but that got replaced by a large cup magnet so it'd easy to plop on the roof of the E when I'm stopped somewhere.
Of course, if you travel away from your home area, you can't just turn on the TV and flip the dial around to see who's in your area now. With DTV, you have to stop and set the tuner back up from scratch before you can even see what channels are available. The plus side is that once you do, the program guide information broadcast with every signal now makes it easier to see what's what.