This kind of friendly, neighborhood bookstore reminds me of the one from the movie You've Got Mail. I'm amazed that a store like this can exist given the influx of Barnes & Noble's around the city (there's one located two blocks from this store).
But Three Lives is a great store - they always have hte best books available and displayed in their windows (I love walking by and seeing what's new and noteworthy).
I'd say the only downsides are the availability of some books and the pricing (they dont' discount heavily like B&N does). Also, sigh, I hate to say it, no cafe and no real sitting areas to enjoy. But the staff is very smart and knowledgeable so if you're a real book lover, then this store is for you. Don't just pass it by.