I have three HDTVs in the house. Each one has a pair of rabbit ears/circular antenna. They are all powered. Most of them are Philips, I think. I don't think that I paid more than $30 for any one of them.
I'm in a pretty good area though. Almost no tall buildings within 20 miles, and in the middle of the Lansing/Saginaw/Detroit triangle (near Flint, so I get that as well). Depending on where I situate my antenna, I can pick up stuff from all three areas, plus Flint.
I've always pondered whether it would be worth it to get a roof-top antenna or whatnot, but I just can't imagine what else I would get. It's not like the broadcast channels ever show anything different, except during non-primetime hours and non-sporting events, when most of the content sucks anyway. I already get like three CBS, two ABC, two NBC, two Fox, and three PBS digital HD stations anyway...I just can't imagine I would get much more value out of anything more complex.