As Percy says, Premier uses to be enough... but some times may happen that a customer preferes making hes/her payment to Paypal through a credit card. Then you will need a Business account. A least, this was the PayPal rule about one year ago, when it happened to me.
You can accept credit card payments with a Premium account, but the person paying you has to have a PayPal account as well. But I think I read somewhere that with a Business account, people can pay with their credit card without needing a PayPal account. However, I think that only applies when you use PayPal in a webshop (using the "Buy Now" buttons). I can't seem to find the appropriate help text on their site any more though, so I can't check this.