Really lovely atmosphere. Wide open with large windows at the front. The restaurant is well-laid out and a pleasure to be in. There is a large, comfortable bar, with bar tables set behind it. It's a great space for a group; there is a lot of room to move around in.
I've frequented Sardine for brunch, lunch, dinner, and happy hour. The happy hour is sort of a let down, Stella and house wines are slightly less expensive, so it's still on the pricey side. For real meals, their food and drinks are fine, but nothing special.
Like most places in Madison, the staff is friendly and warm.