Seanus:
I think isthatu2 has a point. When I do culture classes, I always steer clear of criticism as it's never taken constructively. I throw it in a joking away if anything, like the state of the roads here. It's not my position to come here and criticise anyway.
Actually it's not about criticism but about how you are going to voice it. Lets take those two comments for example:
"I must say, the state of the roads here in Poland are far from being good."
"Dear God, the roads here are as much filthy and crooked as you polish bastards!"
Basically those two statements carry the same message but since they are conveyed in a tottaly different manner they will cause a totally different response.