After you have had an account for several years without any issues, 100% feedback and then decide to sell some stuff, if the end price is over £50, they will take the payment from the buyer, but withold it from you. They take their fees straight away however. You then have to buy postage and send your valuable goods off in good faith before you even see a penny. If the buyer is satisfied and chooses the option to leave feedback, Paypal will then release the money to you. If they choose not to leave feedback, you will wait 45 days! If the buyer has an issue, you won't get the money until the matter is resolved. You won't get your postage back and will have to pay the buyer's return postage.
Go ahead, get a Paypal account, but how many people agree to sell stuff and then send out goods before they have got their payment?
Paypal have recently adopted this policy to save them any inconvenience in the event of a problem.
If my experiences and those of a few other people I know are anything to go by, you'll have a long and protracted load of aggro if things go wrong. Not worth the 4% fees!
If you sell on ebay you will pay a further 10% fees to sell any item. As a seller, if you get a total wingnut buyer, you can't even give them negative feedback now.
Stick to cash is my advice.
If you are going to pay for something, use a credit card where you'll get insurance with your purchases.