AllThingsD:

The launch follows a pilot program in the San Francisco area with more than 150 businesses. The service allows merchants to accept credit and debit cards by swiping them through a card reader attached to an iPhone or iPod touch.

Groupon’s testing period is over. The company tries to position the service as the cheapest option for merchants, but the rate structures it offers are confusing.

There’s a difference between swiped transactions and keyed-in transactions and there’s a third plan for non-Groupon members. The fees not only comprehend a percentage but also a fixed amount for each transaction. It’s a pain to run an estimate of your monthly fees if you’re a merchant. Square’s pricing options are much clearer : either a flat rate per month or a flat percentage on each transaction.

With so many competitors, it’s getting harder and harder for merchants to decide which to adopt, especially which one is the most relevant. User demand and an easy experience will be key selling points.