There used to be a local brewery that made a great root beer around here, but they got bought out by another regional brewery after the owner ran it into the ground. The one that bought them out's root beer tastes like liquid gingerbread and is heavy on the cinnamon. I think it would be great as a float but it doesn't work well on it's own to me. As for more national brands, I would say that I like Goose Island followed by IBC. One of these days I'd like to make my own.