The Mercury was my favorite happy hour spot during the few months between college and fleeing Cleveland. On a return trip, I found things much the way they were when I left a few years ago. Comfy atmosphere. Good drink selection. Quiet happy hour with the bartender at your service.
The scene really picks up later in the evening, so if you want a crowd hold off until 10pm or later. We didn't stick around last night, but apparently women get a free martini and free manicure on Thursday nights. Yeah!
Note on food: They don't serve food at the Mercury, but you can order (at the Mercury bar) from the restaurant next door and have the food delivered.