Originally I thought Amazon Payments was attractive because many people (this could be an over assumption on my part) already purchase items on Amazon and have their credit cards stored with their account. This way, they wouldn't have to take our their credit cards and enter the information again.

That and the trust that Amazon invokes, as opposed to a new startup in which I have no idea how they're processing my credit card.

Maybe I'm an outlier, but I really don't mind paying with paypal. It's rather convenient.

I don't think that the offered payment methods have ever impacted whether or not I actually buy from a particular merchant.

Yes, I refuse to buy anything from a site that only offers paypal, a situation I have run into a few times. My preferred method is generic credit card processing.

I would prefer generic credit card processing.