Couple of reasons I don't/won't use Paypal. My understanding is they are part of/owned by Ebay and, like Ebay, won't allow firearm transactions (altho I think they do allow parts, accessories, etc). I feel very strongly about 2nd amendment rights and try not to do business with those who do not support those rights.
I also understand it is very difficult to get a problem resolved and that there is no recourse to paypal decisions.
Almost all merchants accept a secure credit card transaction. I have always had reasonable success in getting a problem merchant or merchandise dealt with thru the credit card company. If I deal with an individual, as I have several times with CPF members, I just go to the corner convenience store and pay $.49 for a money order. If it's not too much, I'll just send cash.
My info re: Ebay/Paypal is mostly from reading forum posts, etc. If I'm misinformed, plese let me know.