Now, after spending two posts talking up writing groups, I will address the perils of said groups. Be on the lookout for signs that you're in a bad group, or that you might not be using the group properly:
1) Members who don't read the materials - Big pet peeve of mine. There are always going to be weeks where someone will have read everything and still not have very deep notes. That's normal and it's bound to happen from time to time.... but if you notice several consecutive weeks go by without a particular person speaking up, it might be appropriate to talk to them one-on-one and see if they've given your work its due. Now, their silence might be due to something like...
2) The loudest members are the only ones heard. Every discussion has its ebbs and flows, with different people taking the lead. I'm fortunate that my group is generally pretty good about making sure everyone is heard, and that dissenting opinions are debated with respect. Make sure you don't have a bully. Nothing cuts discussions faster than someone who won't let others be heard, or who rudely dismisses the opposing viewpoints of everyone else. A group can't thrive if its members are afraid to express themselves.
3) Group-think. This is the more insidious result of a few loud voices. Eventually the group notes become a Frankenstein's monster. Let's say Person A comes in thinking only "Well, the dialogue can use some punching up and maybe trim a few scenes down." Then Person B expresses that the turning point into the third act is contrived, that the love story makes no sense and keeps repeating the same points over and over again without advancement, and that the problem isn't just that the dialogue is weak - it's that the lead sounds schizophrenic because the plot requires him to act all over the map. At that point, Person A says, "Oh, none of that bugged me before... but it does now!" Then, every other member starts realizing that Person B has a point.
Now, in a lot of cases this could be helpful. You want people to help improve your scripts... but what if Person B is just a relentless nitpicker who never bought into the story for one reason or another - and the other five people were so sucked into your world from the first five pages that these flaws barely occurred to them? Instead of being a celebration of how you got most of the group to suspend disbelief, you now find yourself...
4) Rewriting only to please the group. I've seen this happen before - one member comes in with a promising idea, but the tone and the style is ephemeral enough that each member has a different idea of how the story should be told. Is it a comedy? A thriller? A disturbing indie drama? The script takes on more personalities than Sybil as the notes after each submission push the writer into a different direction.
Rewriting JUST to please the group is a losing prospect. At a certain point, you should have a firm idea of the kind of story you want to tell and stick to it. If you're lucky, most of the group will see the merit in it. If you have a few passionate defenders, then you know you're onto something.
Now if all six people say, "This needs work," then my advice is not an invitation for you to say, "Fuck you! I know this is good!" The bar for script sales is set pretty high, and if the dislike of the script is that high, take it as a portent of how the script will be received in the industry. If you're going out on a limb make sure you've got at least one VERY strong defender with you.
The writers of Mystery Science Theatre 3000 used to say that they didn't stop themselves from writing obscure jokes out of fear that the whole audience wouldn't get it. They said that in cases like that, their attitude was "The RIGHT people will get this."
Groups are wonderful, helpful and great for motivation. Just make sure you know how to use them.