Does anyone have any experience putting a performance air filter in their Bonneville? I'm considering spending the $35 - $50 bucks on a K&N or an AirHog, but I'm wondering if it's worth it.

well I here that they are good but I never had one

Although airhogs are new, they are also good, you can pretty much rely on anything from K&N, you'll get at least 10 extra horse just from putting one in.