There seems to have been a shift lately from Flickr over to 500px so I have been checking it out.
The main complaint with Flickr seems to have come from those photographers who I suppose are raising there game and who have shots that are very professional and aren't overly keen on having there work share the stage with us fumbling amateurs...one quoted that Flickr was a general dumping ground. But then aren't they forgetting that it was there dumping ground too in the beginning.
So as I said I went over and had a look and what I have seen is more professional and yes the standard of photography is high...but its also quite cold, less friendly and to be honest slightly more intimidating.
Perhaps there comes a time when as we grow as photographers we outgrow Flickr, we start to see ourselves as A list and want to hang with the other A listers...only time will tell but for now I will stick with Flickr.