I've been using Paypal for years now and I must say that I have enjoyed the ease of their system. They make receiving money quick.
However, as of late, I have been less than satisfied. They have been continously changing their TOS, adding fees, requiring delviery confirmation, etc...
As a seller, I feel that they should do more to protect us. We pay fees to receive money, we advertise their service, etc. However, in the end, they tend to side with the buyers.
If you're a seller, I'd say beware. However, if you're a buyer, you're pretty safe using Paypal.