We had problems with PayPal as well but at least they called us on the phone and after some hair pulling we were able to come to a reasonable resolution. Google Checkout just stone walls you.
Paypal is to customer service as Microsoft is to security: they appear to have gotten religion after their feet were held to the fire, for all the good that that does them in the tech community's eyes.
For what its worth, I've sold something like $50,000 on Paypal and the handful of issues I've had were resolved with quiet professionalism and reasonable timeliness, in much the same manner that I'd expect from e.g. a bank.
Paypal might be OK from a seller's perspective, but it's pretty abysmal from a customer's perspective.
A couple months ago I was in a financial pinch and one of my bank accounts was overdrawn, while another one had funds in it. I printed a shipping label using Paypal, making sure to use the correct account. When I printed a second shipping label, I assumed it would use the most-recently-used account (the last 4 digits differed by only one number), but it instead defaulted to the overdrawn account.
Only a few minutes later, I noticed this and immediately called Paypal. They said that it was too late to cancel or assign a new source for the payment, even though I told them the payment would be rejected by my bank. I deposited from my other bank account to my Paypal account enough money to cover the charge, and they still couldn't cancel the debit to my overdrawn account. A few days later, I received an email message:
Your bank has declined the funds transfer because your account did not have sufficient funds available. We will automatically re-attempt this transfer in 3 business days. Please fund your bank account immediately to ensure this transaction can be completed.
What?! I already had enough money in my Paypal account to cover the charge, but they instead chose to recharge the same account in 3 days? I called them again as soon as I received this email, but they said they could not change this transaction, that it was their policy and that the process could not be altered. Three days later, lo and behold, it was declined again, and they finally took the money from my Paypal account. Meanwhile, my bank charged me $70 for the two declined charges, all for an under-$4 shipping label.
I will be avoiding Paypal in the future. That kind of inflexibility, poor service, and bad policy combines for an awful customer experience.