Piekielko

Summary
The menu is very traditional, the food quality is almost as good as home cooking in Eastern Europe, beer selection is decent, prices are low even for the neighborhood, service and ambiance are about average for an Eastern European restaurant.

I've been at Piekielko twice, both times with my wife. We found that the place is quieter earlier in the evening if you're going there for the food. Later in the evenings there's more drinking and the ambiance changes from restaurant to sports bar.
We shared the pirogi and ordered the sausage and also the meatballs with mushrooms on the side.
The sausage and pirogi were perfect, the meatballs didn't have the strong taste I'm used to back home but the mushrooms were great. Everything was almost at home cooked quality, so we were very happy with the food.
The price of the food was really cheap, even for Ridgewood, especially since a small salad was included with the main dishes.
The beer selection is typical of what you'd expect at a bar in the area and included Zywiec, which is the most common Polish beer in the neighborhood.
The only thing that people not used to Eastern European service quality might find lacking is the service, which I would say is average for that kind of place but people used to the service in most NY restaurants will probably find lacking. As for me, I consider it good enough for the neighborhood and wasn't expecting much more.
If you are coming late in the evening expect to find people playing Fifa (I think) on a PS and yelling in Polish. So the ambiance is very authentic, but might not be ideal if you're expecting a quiet place to dine. In that case go early before the local crowd gets there.