I completely disagree with the assertion that it is not appropriate to bring up GD reviews, or any other negative aspects about the company - provided it is done with tact. My opinion is based both on having received almost every job I have interviewed for and having conducted dozens of interviews myself.
People forget, an interview is for both parties. It is a chance for the company to know if you are a good fit as well as a chance for you to know if the company is a good fit.
When I am being interview, I often start by saying "I'm going to be as open as I can with you, because I want to be certain that this position is a good fit for both of us." I have never had any negative feedback to that approach. If I'm going to potentially give myself to a company for 8-10 hours a day for a very long time - darn right I can and should be clear in my mind that I will not hate working there in six months. If the interviewers don't like the question (provided I ask it tactfully), they are probably doing me a favor.
From the interviewers perspective, I want the candidate to be certain he or she wants to be there. I don't want to have to train them, watch them leave, and go through the process again. If you have a question - ask it. I've never been offended by a tactful question by an candidate. I have, however, been concerned by candidates that allow themselves to be interrogated for hours without having the fortitude to do some interrogation of their own.
There is a point in which questions can become greedy, and I'm not suggesting that you don't pick your battles. For example, if a engineer fresh out of college is asking about the vacation policy - I see that as a red flag. I don't think that is what the OP is referring to, however.
Hope that helps.
It is funny, the last line was just an after thought and is getting all of the attention : ) . Perhaps it is confusing because I am an engineer and am therefore conducting engineering interviews. Were I HR, I might have a different take. Hope that keeps everyone's head from spinning.