I discovered Critique Circle a year and a half ago upon recommendation of a fellow writer. It's been a wonderful tool for improving my writing and communicating with other writers. There's nothing more motivational then talking to your peers.
I have a 'core group' of about 16 critters who I work with on a regular basis, but I've probably exchanged crits with upwards of 50 or 60 members in the seventeen months I've been a member. I call writing without feedback "writing in a vacuum". I think we have a tendency toward tunnel vision if we don't get input from others. Sometimes things don't translate from mind to paper as clearly as they should. Other times, something may be stated in twenty words that should only take five or six to keep it crisp and concise. Sometimes scenes fall flat. Or emotions that should be turned up to high volume are too muffled. My crit partners have helped me in all these areas.
If you'd like to investigate Critique Circle, here's the site address:
Have fun. :)