I've been to The Corner House on a few occasions, most often to the upstairs bar for drinks while I've been waiting for a table at one of the nearby restaurants. The cocktail list is impressive, and the staff won't hesitate to make something new for you, should you be in the mood for something inventive. While you wait have to wait with eagle-eyes until a couple of seats pop up around one of the teeny, tiny tables, once you settle in with a spot, it's a good spot to people watch and enjoy your drinks. You can't really order food upstairs, other than pizza, which is inventive and delicious. It's the perfect spot to go for a drink on a first date, as the atmosphere is fun and lively, and while it's usually buzzing with a hip, young crowd, I don't think it's pretentious at all.
Only once have I sat downstairs in the restaurant part, as it was during the day and the upstairs bar hadn't opened yet. The atmosphere down there wasn't nearly as good as what's on offer upstairs.