I've only ever had a problem once when someone tried to rip me off of £120 for a phone I was buying for a friend. About 3 weeks later PayPal gave me £100 of it back but I never got the other £20 which I was gutted about.

Never had any problems with the other 40-odd things I've bought though. Never buy anything of anyone who's feedback comes from things such as e-books though.