My quick $.13 (inflation and all). I'm guessing a good thumbnail is what grabs me. I can tell several different artists just by their thumbnails, but that doesn't mean I'll click on everything. I tend to ignore a lot of the "popular" images because they seem to be rehashes (and yes, I'm sure I'm guilty of it as well).

I comment very infrequently, normally because I don't spend a lot of time in the gallery. I spend more time in the forums trying to help out and like the interaction much more.

On a side note, someone said that commenting on others leads to others commenting on yours. I tried that for about a week once, just to see. Guess what. It works. And guess what else. The comments were all of the fluff type: "Great work!" "Beautiful!" "How nice!" I stopped when I saw where it was going and now only comment on something that really strikes me. I can do without an ego stroke.

Now, let's see how many people are offended by my bluntness. ;)