I think most of my theater compatriots don't ask me anymore - because I simply cannot be coy and sidestep comment WHEN ASKED. I don't offer it to say the least.  Too many opinions anyway.  BUT I ALWAYS tell them well ahead of time - and they all seem to have come to know - that IF they ask me....I'll tell them what I think.  Again, it's a personal opinion.  I mean if the audience in general breaks out into a standing O and I don't believe it deserves it, I don't stand.  IF the audience does respond that favorably, then who am I to say otherwise?  WELL....I DO have an opinion always.  And I warn them if they ask, "well what do you think"?  I always say - "do you REALLY WANT to know? Because if you DO, then I'm going to tell you what I think and you may or may not like what I have to say".  It's a disclaimer/qualifier that they know I WILL respond to if they say yes - whether they KNOW what I'm going to say or not - or think they know what I'm going to say.  If asked, and if I don't like something that was done, I WILL say so but always offer an opinion as to what I think is a constructive fix or whatever.  I never shoot someone down because it's my opinion.  I am not harsh and mean, just honest and straight.  I feel I do a disservice if I gloss over it by using some cryptic phrase that tells them nothing.  Just me though.  Maybe that's why my theater friends - real friends - are few.  That or they just don't think they are beyond reproach.