I use Citizens Bank for my merchant services. They charge me WAY less than other providers did. I have a very small volume, so your mileage may vary. But this is the first merchant services provider I've encountered that is actually honest. My only issue was that it is important to specify if you want to get a machine encrypted for debit cards, and to specify if you want a dual-comm machine which means it works over both phone and internet connections. I really like dealing with somebody who is honest after dealing with all these other ripoff artists. I've been all set up for a while, it works basically fine (a couple glitches but the money goes where it's supposed to go), and I'm paying about half what I used to pay.
Easy bank to deal with and great customer service.