A couple of comments ...
Checks of any variety, whether personal check, cashier's check, certified check or money order, are all susceptible to fraudulent use (fraudulent money orders and cashier's checks are actually the tools of choice for most negotiable instrument scams). It can take a month or more for your financial institution to discover the fraud, and the above posts are correct that you cover the loss, not your bank. I won't even accept cash given how easy it is to counterfeit currency and how stupid it is to physically carry a large sum of money in cash to the bank.
I will only accept payment by wire transfer, as this is by far the safest way to receive money. The fee for a wire is typically $20-$25 and the money is in the seller's bank account in two days or less. There is no worrying about whether a check will clear or is fraudulent, or who will pay a 3% fee (which can add up to a lot of money if you're buying or selling expensive gear). As a buyer, I like PayPal because it allows me to immediately "seal the deal", but as a seller, I tend to be selling fairly valuable gear and I am not going to be dealing with any 3% fee or fears of forged checks, etc.