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But seriously - I've heard of browser specific web app using IE's "unique" features to make good-looking graphic heavy UI's etc but I've not seen any for Opera. You might be reaching into territory where none have gone before - so you might find that if you hit a wall, no one will be able to help you. This isn't my area of expertise though, so I might just be completely wrong.
Is there a strong dev. community for this kind of thing in Opera? You might want to check it out first.