Paypal are excellent and in my experience extremely reliable. I have never had a problem though if you sell abroad be prepared to send your item/s so it is traceable by post.
You can deposit money paid to you from paypal free to your bank account (£50 or more is free of fees and it takes about 5 -7 working days).
They do of course have fees for the service they provide and like ebay of which they are now owned.
Read the conditions when you sign up it pays to avoid misunderstandings you'd be surprised how many people don't and then complain because they have had a bad experience. They are very reliable in my experience (4 years).
Cheques are 'old hat@ and the sooner we get rid of them the better.
On a general note - Never ever respond to email requesting your login details PIN numbers etc reportedly from paypal, ebay or your bank etc.
They will never ask for this information by email.