First of all, there's Penn Jillette's relentless libertarianism. Now, it's pretty safe to say that I used to fairly idolize Penn Jillette. He was a big goofy-looking dude (he's far and away the winner in the 'celebrity I most resemble' sweepstakes, if other people are any guide) who knew a bunch of cool tricks, was fearless and outspoken about his political and philosophical views, he had a low tolerance for obvious nonsense, and he was obsessed with Uma Thurman; what's not to love? Unfortunately, as time has gone on, he's displayed some tendencies that are less lovable. He's a bit of a blowhard, as are all really opinionated people, but with a nasty edge of self-righteousness; he's polyamorous, which is fine, but always brings me down when people talk about it a lot, which he does; and he's a die-hard ultra-libertarian, a devotee of Ayn Rand, and (!) a senior fellow at the Cato Institute. This comes through way too often in the show; he's quick to talk up the lack of peer review when he's debunking intelligent design (as well he should), but he's equally quick to ignore the presence of peer review when he's debunking global warming. He's also constantly critical of people who cynically peddle nonsense in order to make a buck, but it seems not to have occurred to him that as much money can be made off of environmentalism, recycling, and alternative fuels, there's a lot more to be made off of the industries they're meant to correct, and that just maybe all the people who are saying global warming is a myth have something to gain from their stance as well. (To his credit, he's owned up to having his head up his ass on second-hand smoke.) I know his standard disclaimer -- "We're as biased as anyone, but at least we admit it" -- but I don't see that as any less of a cop-out than if an evangelical said it.
Beyond that, though, it can be an enjoyable show -- depending on who's writing it. BS's writing staff is wildly inconsistent, coming up with hilarious and insightful lines and cutting jokes one episode and wheezing out hoary gags, puns, and one-liners that seem like they belong on Animal Planet home video shows the next. I want to like the show -- I mean, I really want to, not just because I like Penn & Teller, but also because it's one of the few skeptical voices in mass media -- but in the end, I really don't.