Dunkin Donuts is the best. I come here in the mornings of the weekdays and, despite the massive avalanche of people, the employees are up to the task, friendly and efficient. They receive orders long before they pay for everything to start and I never expect much to drink my drink despite the large number of people.
Congratulations to the employees here: you can say that they care about their customers and make a great effort to bring things to perfection, and that can be hard to find in a cafe that deals with the rush of the morning!