It isn’t a good place to really improve your photography skills in my opinion.
To clarify this, it is certainly possible to improve your techniques and editing skills by viewing others photos and asking questions. The big pitfall is that when you post work up for critique or just to show it off you get a barrage of positive comments along the lines of ‘great photo!’ or similar. On the one hand this is great if you like to have your ego stroked, but on the other the lack of negative or any real constructive criticism doesn’t really push you to fix or improve on the small things that could really make the photos fantastic.
Now I’m not saying that I’m an expert photographer, far from it. I would love to have people honestly critique my photos more often so I can improve. It is only because I am so well aware that I have a long way to go that I push myself to try improve each time I go out with my camera. If I was to rely solely on critique from Flickr I could be mistaken into thinking that I’m a pro photographer and should be working for National Geographic or something along those lines.
Photography and art is always a very personal preference in what you enjoy, but the constant positive reinforcement without constructive criticism won’t help you improve unless you are aware this is happening and factor this in to your ever continuing development as a photographer.