Fred, I agree with John. My best image is the one I haven't taken yet...and with my images critiqued I bring alot of the information/suggestions along with me on the field to try to get that image. I don't have to agree with everything and everyone 100%, but it gives me more incentive to push myself and grow as a photographer - and I do learn tons from the collective output.
On the flip side of the BPN experience is critiquing others' images as well. You'll find you'll get alot out of your membership this way too. When critiquing other peoples' images you tend to start bringing that with you in the field too and start self-consciously asking yourself questions before triggering the shutter button (e.g. "why am I composing this way?" "perhaps I should wait for the subject to turn around?" or "maybe I should get lower?"). Posting AND critiquing is a win-win situation
