Really surprising to see only a few reviews for such a great restaurant. Wife and I happened to be around this area after visiting the Duquesne Incline and boy was I glad to have found this place.
French food at its finest. They are best known for their "Tartine" which is really an open faced sandwich that I highly recommend. My wife got the Strawberry tartine and that was absolutely delicious. I got the Croque Monsier, which was equally delicious - they had this thick sliced ham with nice thick cheese. Highly recommended. Their quiches and desserts look good too, but didn't try this.
Also wanted to point out how nice the owner himself was (or at least I'm assuming it's the owner). He personally greets each customer as they walk in and thanks each customer when they leave. That's great service and a testament to the restaurant.
Other advice:
CASH only
Street Parking
Closes early - check their hours
As others have mentioned - there is a dog that walks around - if you don't like that, you might want to consider somewhere else