I recommend Ariel ((Cons)
With Ariel, it is pricey.(Pros)
the inside is small but cosy, the Jewish music is great along with the food and it's location next to the night-life.
Another two places, but they are not in Krakow centre but I just thought of are:
Number one and my favourite restaurant to eat in is Niepolomice Castle
I posted some photos here
it is 25KM from Krakow market square.(Pros)
It's a classy castle and not too pricey at all, Ariel is probably more expensive and the food is delicioussss (turkey neck :). And it's in a wonderfully restored castle, with beautiful surroundings and lots to see and do besides eating.
One more place that I like is Karczma Bida(Cons)
There is nothing else to see there that I know of and it's about 20KM from the market square, on the Zakopanska road (towards Zakopane).(Pros)
It's at least a hundred year old cottage style restaurant with a very Polish interior and traditional Polish food, without being over the top at a reasonable price.