I signed up for an “offiical” merchant account at Charge.com which lead to me getting an authorize.net account. However it turns out that Authorize.net handles the credit card purchase, but used another company (which is what charge.com was selling in the first place) to then deposit my money. It turns out that if you want to sell American Express, it costs more. If you want to store customer data, have reoccurring charges, etc it was more.
Then I changed my focus by adding podcast equipment sales to my website. My sales went from $50-100 a sale to $1000 a sale. That threw up many red flags and in a nutshell the people a cynergy data fired me as a merchant as I was too much of a risk (because I was selling things I didn't own). The bad news is Authorize.net then charged me for another month to the tune of $130.
In the end I went back to PayPal, and everything is fine. I usually tell you what tools I find that I like. This week, I'm telling you that unless you're going to have a HUGE amount of sales, a merchant account may not pay for itself.