As ferndaleflyer has said this subject has been
Beat To Death :B
But..I put one on my RV for 2 reasons, the bat wing was only marginal and the addition of the Wing Man was not an option because of it's size, it would not clear my A/C on the roof. Where the Jack would.

I have had great luck with it and compared it with others in our camping group that had the BatMan, when out togather and got as good or better reception as they did.
I found a new one that is not much bigger and fits in the same space.
It is
The Rayzar][IMG]http://i.imgur.com/TgLwTbbl.jpg" height=220> In a non scientific test I was able to get 20 more channels from it when doing a scan on my TV. One nice thing about it is, its Multi Directional.
After I bought it and used it a while, I found a discussion
Here on the NET about it.