What Makes a Good Skin/Icon/Cursor/Theme?
Of course, there are some things that almost everyone recognizes as high quality. Skins like eminence and Jaluran seem to be enjoying pretty wide-spread acceptance by the community, at least judging by the number of downloads and comments. But what is it about these two skins, which are very different in general style, that everyone likes so much? Personal tastes aside, what makes a skin, an icon, a theme etc. "good"?
Currently, I'm running eminence by rjsmith2007 for my blind, and Mormegil's Apogee icon suite. Hippy's Magic 8 Ball often graces my desktop and I have ObjectDock Plus running with the standard skin (because I can't find a good one for it). All of the enhancements I actually run on my system tend to be of the clean/minimalist style. Soft, clean edges, nothing extra/unnecessary generally. That's the style I like. But then again, I love MikeB314's Old Republic skin, which is generally a lot busier than I usually like.
What is it about these different skins? Is it their clean and well drawn graphics? Is it the interesting placement of borders? Is it the color schemes that do it?
What do YOU think are the essential elements to any skin, icon, theme etc? What separates the OK from the great? What are the things you always look for in the content you download?

I can't really tell why ppl like what ppl use, I just design to my liking. If I dont like I dont produce or upload...If ppl like it its a plus to me..if ppl dont...and did not tell my why he/she dont like it...I cant really tell why....but one thing for sure ppl preference swings 360 deg all the time...so if ppl dont like it....well at least i like it. And I assume most of skin designers here think this way too...??