Don't be Microsoft and focus on "prettiness". Things like graphics, gradients and animations should be added because they directly help someone understand what will/is/did happen in your plugin; not for show, not to be pretty.
Interesting point. I hadn't realized that having a good looking interface was actually separate from having an easy to use one.
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I'm going to have to keep that in mind going forward, because now that I think about it, I think I've often made graphical decisions based solely on what looks good rather than what will help the user naturally understand how it works. I guess my apps are the graphical equivalence of Vista or 7...