I've been watching Penn & Teller's "Bull****" since its inception and I think it's a great show. But.
There's always a but.
P&T themselves show a significant amount of bias centered around a few key areas. The show has a very strong libertarian/privitization sort of slant. Now, P&T themselves also admit in the intro to the first show that they are "biased as all ****" themselves. Which is fine. But they really should make it part of the setup in every episode. The show suffers from two traits: First, P&T tend to grossly oversimplify the topic at hand in most cases. Second, they take too seriously their role of playing devil's advocate to the point that in some cases they themselves start resorting to the same tactics as their opponents. This goes hand in hand with the oversimplification in most cases. Usually it takes the form of omitting or working around otherwise factual data that would contradict or just plain complicate P&T's own argument.
The gun control episode is one of their finest works. No complaints there, and no complaints about their shows on the war on (some) drugs, mystics, ESP, aliens, and other "duh" sort of topics.
However.
In particular, the recycling episode grossly oversimplifies the situation and while arguing against recycling on some very valid economic terms it sidesteps many other valid points. The bible episode, as another example, is cheeky and entertaining but not in any way balanced or even completely factual. I'm not disagreeing with thier overall message - I'm disagreeing with Penn's line "it is fair to say that the bible contains equal parts fact, history, and pizza." Which is flagrantly incorrect. In cutting together their "interview" with their bible expert (his name escapes me) they leave in his line about the bible containing some verifiable, currently considered factual passages. They do this only to contrast some of his other semi-nutball views about biblical miracles while completely ignoring the fact that once you get beyond the passages about parting seas, blowing up cities, ten plagues, and so forth there are whole (admittedly boring) chapters about who was king where, who waged war against who and who won.
Which scholars are slowly verifying through other, non-biblical, non-religous evidence. But since I knew this and they deliberately glossed over it, it made me look at the series again with a more critical eye.
You should bring your salt shaker, too. Penn & Teller are good guys and they're on our side, for the most part, but they aren't oracles any more than anyone else on this planet.