I am a big fan of Intuit's financial products; until recently, I used their merchant services for my infrequent credit card processing. The GoPayment system is an improvement in terms of fees and convenience. It comes with a free Roam reader when you sign up for a new account, that is similar to the Square and that fits in your phone's audio jack, but I didn't test that Intuit can also work with a second type of reader called Mophie that sells for $80.
If you go to Intuit's Web site, you'll find two plans: one with no fees but higher rates per transaction (2.7 percent plus 15 cents for swiped cards, 3.7 percent plus 15 cents for manually entered numbers) and one for higher transaction rates that will cost $13 a month with lower fees (1.7 percent and 2.7 percent plus 30 cents per transaction, respectively). Either plan includes the free Roam reader. This is a better deal than the Online Terminal plan I used to use, which didn't include the reader. Anyone who is still using that plan should switch and get lower transaction fees, even if they don't have an iPhone. If you use Quickbooks to run your business, Intuit does a nice job integrating your merchant account payments with that software, so you don't have to re-enter your transactions. Intuit has a great series of online demos and tutorials on their Web site, along with extensive documentation.
There are two different Mophie physical readers: one for the iPhone 3 series and one for the iPhone 4 series. This is because the reader is actually integrated into a protective case that completely surrounds the phone, unlike the PayAnywhere.com reader that just goes halfway around the circumference. Intuit can set up multiple users on your iPhone too.
Of the three services examined here, the Intuit is the only one that accepts JCBcards, which could be important to you. Their plans also work with Visa, MasterCard, Discover, and Amex, and Intuit offers phone support.
Your cash register, your phone
Any of these readers is definitely the next step for retailers and offer tremendous utility and flexibility in payment processing. The two biggest issues will be if you have the right iPhone version and can anticipate your fee schedule for your charges. If you do a lot of charges, then the Intuit $13 a month plan will quickly pay for itself. I liked the simplicity of Square's setup and use, but the additional features of Intuit's reader might be useful. If you are the type of person that likes telephone support, then PayAnywhere.com is the most responsive.