I have been going to the Abbey Pub for a number of years now, and it is a gem on the Upper West Side. Their burgers are excellent. When they have it as a special, their salad with avocado and olives is delicious, and good to share with someone as an appetizer.
Their beer selection is very good, and includes a number of lesser-known beers. Great to go to on a Sunday or Monday night for a quiet drink or bite to eat, especially if you get a seat in the booths.
Service has been up and down - their regular waitstaff is solid, but some of the other servers who have come and gone could be better.
Pros: Beer selection, Burgers, Mellow
Cons: Service, sometimes, Not much to look at.