Just as seen-by (link) it only shows work that has been screened by the 'staff'. seen-by really shows interesting things, but I have the feeling that Onexposure puts the bar a little higher. Maybe it's just my personal taste, but I literally chocked over my food when I first noticed the density of perfect work on that page :-)
For the first time since a long while I actually felt inspired to go out and do something creative with my camera, which might have also to do with the fact that this humid summer is finally vanishing, but that's another story.
So, besides being impressed, what is my personal experience with onexposure so far? I uploaded one of my pictures (Stairway to Hell) and gave a little artistic description. It got accepted, which was followed by a warm welcome by several other users.
You can find it here (link).
An for completeness: My current seen-by portfolio is here (link).