One of the other things is that with the new, detailed seller rating, even if you waited 48 / 72 hrs or so to ship the item after the payment was received (which is the usual amount of times it takes for Paypal to reverse or hold the transaction), you are going to get marked down on your shipping speed.
Paypal and ebay have sellers over a barrel I think. I sell a lot on ebay and have done for over 8 years. In that time, I have had 5 reversed transactions.....but 3 of those have been in the last 6 weeks. In all of those instances, Paypal didn't give a flying monkeys, even when I had emails saying item received and positive feedback left. The system sucks but yet I agree with the other posted who said if you don't accept it, your sales drop.