You may want to consider installing a front-brake as well as using a coaster brake. Coasters are good fun, but aren't known for their stopping power. You'll also encounter the same problems that fixed-gear riders come across with crankarm placement when you are stopped at a stoplight, etc. You can't backpedal your cranks to a good "starting position" with a coaster brake hub since backpedaling wou ld activate the brake.
But it looks like NYC bikes is using Shimano parts so I wouldn't worry too much about getting replacement parts or service for them (older coasters have this problem), so that's good.
Since it's not my money being spent, I encourage you to try it out! I would be interested in hearing the results of coaster-brake stopping power. If it seems good, I'll grab myself a pair of coaster wheels!