PayPal protects both Buyer and the Seller. If the buyer, after receiving the domain name, files a dispute of non-receipt, you have the sufficient transfer emails from the Registrar that will protect you, you can produce these emails to Paypal, they will take these into consideration. So far, I have not come across a single incident where a Seller claims that he refunded the money as well as lost the domain name. I have been a PayPal member for years, and they have been very very fair in their investigations, be it buyer or seller.
Of course, there are other disadvantages with Paypal, like higher commissions they charge. We need to pay more than 5% as commission for all Receipts. This is very very disturbing for small traders, where their profits itself is not even 5% at all. PayPal should reduce the charges.