Critiques:    The Good, Bad and Ugly
While I would be the first to tell anyone that getting and giving critiques is one of the best ways to improve your writing, I would say so with one big caveat: All critiques are not created equal. And further, evaluating a critique is more art than science.
The first (or second or third...) time you run a story through a critique group, particularly a large group, can be overwhelming. All those comments, and some of them contradictory. This is the point where some writers give up on a story, thinking it is unredeemably bad.
One effective means of dealing with conflicting critiques is to look for trends. While a consensus is unlikely among any group of critiquers, there will usually be recurring issues within a story. For example, several of your critiquers may not understand the significance of a scene. Or perhaps a few find your main protagonist weak.
Beyond that...things get a bit fuzzier. Never dismiss a comment immediately, even if it bugs you. Sometimes the advice that stings the most is most beneficial. What doesn't kill can only make your stronger and all that. But, by no means does that mean that every critiquer's suggestions should be taken to heart.
Some critiques are going to be more useful than others. In part, this is a function of the tastes of the critiquer. Ideally, the person reviewing your work will be as impartial as possible, putting aside his or her literary preferences and evaluating the story based on set criterion--plot, pacing, etc.
But critiquers are human, not machine. A reader of hard, idea-driven SF may have a hard time mustering the interest to read a light contemporary romance, much less critique it objectively. Though that is an extreme example, keep in mind that even within a genre, there are many subgenres, and readers thereof. A fan of epic fantasy may find contemporary fantasy mundane and uninteresting and their critique will be colored accordingly. If you are lucky, they will state this at the beginning of the critique--"I don't like contemporary fantasy." Often, however, you gotta read between the lines.
And then there are the few special types of critiquers I have listed below. My contention with the critiquers listed below is not their opinion, but rather that they are "one issue wonders," rarely addressing the useful stuff--plot, dialogue, pacing, etc.
The Agenda Critiquer
This kind of critiquer might also be called the "activist." They often spend much, if not all, of the critique complaining about some social ill or supposed misinformation contained in your manuscript. This differs from someone who is simply pointing out a factual error, however. (Thank your lucky stars for a critiquer who corrects a factual error.)
Let's say your manuscript features a chain-smoking protagonist. Better yet, his habit is instrumental in the plot. E.g., his carelessly tossed cigarette butts lead the slavering monster to his doorstep. One version of the agenda critiquer will complain that your characterization stereotypes all smokers, making it seem as though they are all callus slobs. A second version will spout smoking related death statistics and deride you for glamorizing smoking.
If your goal is to write safe, "nice" fiction, that never pisses anyone off, then by all means, revise to placate the "activist."
But "real" characters, that kind that resonate with the reader have bad habits. They think nasty thoughts. They scratch their bums and flick their cigarette butts out the window. They drive over the speed limit and steal grapes from the vegetable bin in the grocer store. Interesting characters invariably upset someone. And that's a good thing.
Mr. Originality
I don't know if this attitude is found in other genres--mystery, romance, thriller--but there is a segment of the SF/F/H genre that seems to despise the very things that bring many readers into the genres. If you write vampires, elves, or other well-trodden aspects of speculative fiction, expect the occasional yahoo to insist "this type of fiction is dead." (I always imagine them writing this with their chin lifted, mouth set in a stern, officious line.)
Worst yet, they will tell you that "no editor will touch" a story featuring this type of character. Oh, really?
Like it or not, people gravitate toward familiar story lines and character types because they resonate emotionally on some level. Take romance, for example. The notion of two people finding each other and somehow, despite all the b.s. life throws at them, riding off into the sunset together, is not new. But it sells (the romance market is one of the healthiest). It's a fantasy. No, it rarely deals with the aftermath--marriage, kids--but who cares? It's fun, a few hundred pages of escapism.
Editors are buying stories with elves, werewolves and vampires, thieves-with-hearts-of gold, and orphans who become kings. Why? Because they sell. Writing is a business folks.
In defense of vampires, for example, I'll point out the inclusion of Robin McKinney's Sunshine in "Locus"'s Recommended Reads for 2003. Vampire fiction by Laurell K. Hamilton is consistently at the top of Amazon's top seller list. Ditto Charlaine Harris's Southern Vampire Series.
Now I will admit that stories featuring literary tropes can easily slide off the derivative slope. That is, sound exactly like the last published novel in the sub-genre, only the names have been changed.
The biggest problem with archetypes is that they can result in lazy characterization. For example, the author assumes that "everyone" knows how an elf should behave, and doesn't bother to actually build a character. Their character's sole attributes are those of the stereotypical [Tolkeinesque] elf. Tall, blond, graceful, and good. Yuck.
Like archetypes? Write 'em. But invest them with unique characteristics, make them your own. Do all elves have to be good? How about a vegetarian werewolf? A vampire with an allergy to blood?
The Gatekeeper
This type of critiquer believes it is their job to keep out the riff-raff. A good adjective for this type of critiquer is "tactless." They use the word "you" liberally, and forget the "critique the manuscript, not the author," rule.
A critique from The Gatekeeper may sound something like this:
"This is the worst manuscript I have ever read. You have written a story that is utterly derivative. Your grammar is atrocious. Before you write any more fiction you must take a class in Basic English composition. I found numerous typos in this manuscript and your lack of attention to detail insults me as a critiquer."
The above is cobbled together from critiques I've seen given to other people's stories. So far, I haven't incurred the wrath of a Gatekeeper. I have elephant hide and my response to such a critique would be a brief note--"Thank you for critiquing my story"--and I'd get on with my life.
But this type of critique can be damaging to someone who is just starting out. Frankly, it's cruel. If you run into the Gatekeeper, remember that writing is an art form and thus subjective. Don't let anyone make you feel bad about your writing. Pity the critiquer for the spiteful person they are and then...get back to writing.
In Closing
If you get a particularly troublesome critique, get up and do something else. Clean house, walk the dog, watch television, etc. (I go muck out the horse paddock.) If, after your break, you still find little worth in the person's comments, then move on. (Oddly enough, after a cool down period, I often find myself agreeing with the critiquer. Often, but not always.) The point of a critique is to get an honest appraisal of your work. But any critique will be subjective. You can't please everyone and it's a waste of time to try.