I do a lot of selling online, and Paypal has been entirely safe in my experience. Never buy something using the "gift" option, as others have said, you lose buyer protection when do you so. Paypal does charge 3 percent, but if I use my Amex card through Paypal, Paypal ends up having to pay that 3% back to Amex, so they don't make that much money on the fees. eBay on the other hand has multiple fees, of which the 3% is a very minor part.
For those who charge an additional 3% when you sell items outside eBay, it is still a violation of the user agreement. Though it seldom happens, a buyer can complain about the extra fee, and if he includes a copy of your ad along with the invoice for his payment, you are likely to end up with a hold on your account until you sort things out with Paypal. It's best to figure in the 3% into your sale price and not mention it separately.