I've been using them since I first started using eBay, for buying and selling stuff, in 2003.
Pros:
1. Pretty secure. I've upgraded to their Business Account, and have the PayPal debit card, etc. No problems with my bank/credit card accounts being hacked to date, but there's always a first time.
2. More and more online businesses are accepting PayPal payment. That in conjunction with the PayPal debit card gives me a lot of flexibility.
3. PayPal's Dispute Resolution seems to work very well, too. I've had to use it three times so far, as both a buyer and seller, and have had favorable results each time.
Cons:
1. They charge for each transaction. Over the course of many transactions, it adds up.
2. They're a subsidiary of eBay. Take that for what it's worth, but eBay is very anti-gun, and they're somewhat proactive on preventing gun-related transactions. I was doing a great business selling reloadable brass on eBay until they banned it after the VA Tech shootings.
3. Having said that, I've bought and sold tons of gun-related stuff on eBay, and sent and received funds for such using PayPal. Just camouflage the transaction descriptions, like everybody else does. What they don't know won't hurt them.
4. I personally enjoy using an anti-gun company and subsidiary to further my pro-gun activities. YMMV, of course.