These guys were great! Super friendly, answered all my questions, made good suggestions, and fitted the bike I rented to my size (handlebars, seat, etc.) They even threw in a phone holder as I was traveling via bike out into the countryside (15-20 km).
I rented for the two weeks I was there, and they offered on-call service if I had any problems on the route.
I would definitely rent from them if ever I am again in Krakow.