Just days after unleashing the bladder-busting, 31-ounce “trenta” size on America, Starbucks has announced that users of iPhones and Blackberries will be able to pay for their caffeine fix with their smartphones.

S’bucks tested the system in a handful of markets, including NYC, during the last half of 2010. Now the java giant is set to roll it out to all 6,800 company-run stores and the 1,000+ Starbucks counters set up in various Target stores around the country.

To use the pay-by-phone system, customers must download a free app to their iPhone (or iPod Touch) or suitable Blackberry (an Android version is in the offing). The app effectively replaces the customer’s plastic Starbucks Card, allowing them to pay by waving their phone’s screen in front of a scanner.

The app also allows customers to monitor the amount available on their card and add cash if needed.

The question is: Does this actually make the process faster than swiping a credit card or paying in cash?

If you’ve tried the Starbucks mobile-pay system, give us your feedback in the comments.

Starbucks: Mobile payments coming to stores [Forbes]

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