I'm a U of C student who frequently ventures into the city, so I pass Cafe 57 on my way to the #6 bus. Now, I'm no coffee aficionado, but I do know a good cup when I have one, and I've had many -- including one from Z&H (which I think is madly overhyped and overpriced, but that's another story). The cappuccino I got from Cafe 57 was a work of pure artistry. Not only was the coffee full-bodied and rich and the foam on top creamy and delicious, but the owner (I believe her name is Belinda?) clearly paid attention to the aesthetic details and ensured that the coffee looked as beautiful as it tasted. She was so sweet, too, and paid really nice compliments to her customers!
Pros: Intelligentsia coffee (SO MUCH BETTER than Z&H's Metropolis coffee), great service, homey vibe, unbeatable location (the only complaint I have with this is that it's pretty far from the heart of the U of C campus)
Cons: a little pricey, but maybe that's because I can easily find cheaper (but not as good) coffee on campus; cafe a little small
All in all, this is most definitely a Hyde Park staple, as much as Medici's is. I would come here every day if it were located on the campus itself. In fact, it's probably a good thing that it's located a little far -- makes going there a treat! WORTH EVERY PENNY.