Very interesting thread, good discussion and many valuable points.

There is one point that I'm missing in some way or another, and that I would like to throw into the debate.
A lot of the replies talk about improving, getting better, growing, approval, etc. But all that seems to stand in relation to what I would call the 'cosmetic' side of photography: composition, colors, tones, general appeal, focus... all very valid and 'important' points when it comes to evaluating photographs.
But the one thing that I value more than all the others in an image would be 'truth'... translate that as 'individuality, personality, honesty and sincerity'.
Somehow I feel that, even if you managed to get all the cosmetic aspects right, it was all done pretty much in vain if you somehow failed to achieve that one last point: truth. I'll try to give an example from experience:

On an other site, I posted a photo in which I deliberately did everything to make the image appealing to a broad audience. Sometimes, after a period of not getting much interest for my usual images, I feel tempted to do that... I payed attention to all the 'cosmetic' aspects, and at first it seemed to pay off: the first comment said that it was one of the best winter scenes to grace the site in a long time. But here comes the point: the second comment just literally said: "You want my opinion? This is sooo not you, Geert..."
Both comments were, I think, sincere. But the second one was all the more valuable, because it said so much more about the commenter's appreciation for the sincerity, individuality and honesty displayed in the other images that I had already posted on that site.

Morale of the story:

Cosmetics are fine. They can help you get somewhere. But when you get there, it helps to have a foundation that you're confident about, so the cosmetics don't fall off... ;o)

We do not see things as they are. ǝɹɐ ǝʍ sɐ sƃuıɥʇ ǝǝs ǝʍ