We booked Lenka and Jaroslav's apartment knowing nothing about Prague or where to stay, but looking back, I can't imagine a better location or place to stay. It is literally a stones throw from Charles Bridge, but on the less touristy (imho) lesser town side. It's just around the corner from the main drag on a narrow little cobblestone street, so while it's close to the sites it's also quiet and away from the crowds. There are lots of restaurants very close by, including some favored by locals.
The apartment itself was clean, comfy and roomy, and the coffee and press pot were a nice touch. There is a cafe downstairs in the courtyard and a very cool bar in the basement that plays great music, plus live music a couple nights a week.
Jaroslav was incredibly responsive and also helped us with dinner reservations for my wife's 50th bday. We'll definitely look to stay here again when we're back in Prague.