Wow, I could have written several of the messages in this thread, although I'd probably make more typos.
I find online critique groups have been of no help. Some are clearly better than others, and of course a whole lot depends on who's in the group, but the logistics of marking a manuscript for cyberspace are pretty daunting and the qualifications of some who critique highly questionable. I've done quite a few critiques online but never received one that I found helpful. Meh.
A single genre or very closely related genres (thriller, suspense, and mystery, for instance) is vital, IMO. I'm most certainly not qualified to give meaningful input for genres I don't even read. (I'm likely to suggest the raven-haired beauty needs a bomb strapped to her back, or a knife in her hand, more than she needs the handsome veterinarian.)
Group dynamics matter a lot. My present group is very small but works well. The larger group used to work until a particularly strong-willed member joined, after which it always divided on 'party lines,' allowing personal feelings about the authors to influence their critique. Don't slam my manuscript because you're Sally's ally--slam it because it's weak.
Rules. Gotta have 'em. Sometimes we choose to bend or break them, but we always return to them. We found it vital to have a system in place for dealing with problems before they arose, and it worked for many years, failed once, and now works again.
Diversity of members is ideal, but hard to achieve. It's important to us for everyone to be writing at a similar level of expertise, in similar genres, and our efforts to recruit people different from ourselves haven't produced anyone who writes at a similar level. (Please note that it isn't total elitism, but that we expect members to be able to construct and punctuate a sentence.) We, too, have a hard time recruiting men--one moved away just because of some job, and another died on us. Like those are valid excuses!
Being in a group, whether it's a writers' group or a critique group, creates expectations that all members will write. For some, this is necessary and helpful. The best groups' meetings break up with members rushing home to write, freshly enthusiastic.
The social aspect is important. Were it not for writing groups, there would have been periods in which I'd have had no one to ask questions about writing, publishing, etc. (Now I have all of you, of course--thanks!)
Of course, the writer has to rely on his or her own judgment about what changes to make to the manuscript based on input from a group. In the end, whose name goes on it?
Maryn, whose real name doesn't go on many