Having read the guide written by tomstoolchest, I feel I should point out Paypal's good points. I never buy on Ebay unless the seller accepts Paypal, for the following reasons:
I have bought several separate items, from different sellers, which have either failed to arrive or were of very poor quality, so I asked the seller for a refund in each case. Most sellers do not hesitate, but one or two use any means at their disposal to avoid making a refund.
In every case, when I contacted Paypal for help, I received an immediate refund and one seller was "struck off" Ebay's site for persistent offences.
Paypal has never let me down yet!