I use Paypal more for purchasing securely from websites that support it than I do selling on Ebay these days. Using PP to purchase something is pretty simple. You will get redirected from the site you're shopping on to PP and you can check out. You can opt to have the money transferred from your bank account or put on your credit card (my method of payment for extra payment). After that it's pretty much the same as any other place. You get a confirmation of your payment. Refunds are a little more of a pain as your account usually has to be refunded and the money is put into your PP account which you then have to transfer back into your bank account. If you paid with credit card
AFAIK there is no way to get a direct credit back to your card.
I no longer sell through Ebay because it has become too problematic. I won't get into all the issues of buyers filing complaints and trying to screw over sellers and PP being setup more to be in favor of the buyer and not the seller because there are too many threads like that. My biggest problem with why I stopped selling was because unless they changed things, a lot of the time when you get paid buy the buyer, PayPal will choose to hold your money and force you to ship the item on your dime. They won't release the money until the item has been delivered and it can be proved with tracking, until the buyer gives you positive feedback or after 21 days. They claim they only do this for "high risk" transactions, but I got to a point to where they were doing this to me on every transaction. Most buyers don't leave feedback, and unless you ship something by UPS or Fedex within the U.S. there delivery confirmation never worked, so most of the time I had to wait 21 days to get my money.
Sorry for the long post. But long story short, for non-Ebay transactions, I've never had a problem and especially if I do business with someone here I prefer it. But for Ebay I stay away from it all together unless I'm buying something.