I actually took this exact class - minus the sci-fi part. But the 2 a week, roundtable discussion plus written feedback bits were exactly the same. So having been on both sides of the fence, I'd say definitely be honest but ease off on the brutal. At least in the round table. I know it was easier for me to accept some of the harsher criticisms to my stories when they were written out than talked about in class. I didn't feel like I was under a microscope and I was able to get go of my defensiveness enough to absorb the critiques for what they were.

That being said, I appreciate people who were blunt about what they didn't like more than the ones trying to blow sunshine up my ass about my story. Telling me only the things they liked was supremely unhelpful.