Hers is one of a growing number of coffee bars that have opened recently around the country, particularly in New York. Instead of idling at a chair, customers at these establishments stand or perch on a stool to down a cappuccino or an iced coffee at the counter. By doing away with the comfy seats, roomy tables and working outlets that many customers now seem to believe are included in the price of a macchiato, the new coffee bars challenge the archetypal American cafe.