Having just read Old Kitty's flash fiction story (she has the link on her post in case anyone wants to read it, and you should), it brings to mind something about peer group reviews.
Here's the truth: the better your work is the pickier readers will be. Old Kitty's piece was excellent, near to perfect, and thus the responses were "don't like the ending, it's weak." (Yes the ending was a bit weak, but that's an easy fix.)
Reason being, if your work elicits an emotional response (which all good writing must do), the peer reviewers feel that response, thus noticing a section that's not producing the same response. It stands out against the brilliance of the other and is pointed out as the weak spot.
Here's the other truth: If your entire work is weak, you will get general feel-good praise rather than being picked apart. Your reviewers, not wanting to be rude, will say, "that's good!" and "I like the ________ part!"
So if you're getting a lot of the "pickiness" take it as a positive! And if you're getting the general feel-good praise, take that as a negative. It means your work isn't eliciting enough of an emotional response for anyone to care if you fix the ending or not.
"Never give up. And most importantly, be true to yourself. Write from your heart, in your own voice, and about what you believe in." ~ Louise Brown
"Write something to suit yourself and many people will like it; write something to suit everybody and scarcely anyone will care for it." ~Jesse Stuart
"A writer's job is to take one thing and make it stand for twenty." ~ Virginia Woolf