I've used paypal for over a year and while my throughput is not great (a purchase or two a month), I've never had problem with payment or delivery.

Just make sure that the person that installs paypal on your site knows what they are doing (this is not DIY territory) and then do several test runs on your system: set up a 1 penny or 1 dollar item and buy and sell and deliver and go through the whole process a few times.

Also be sure to get the minimum you need. When you sign up to take payments by paypal, there is a whole bunch of options that can get expensive and we don't need (like telephone support).