If we're playing that game, I suspect the reason it doesn't show up in Opera is that Opera's JS engine is faster. ;-)
Perhaps I'm wrong. Maybe my code is getting run perfectly, but it's just happening so blazingly fast that it doesn't affect anything at all. In which case, I'd still give Opera the big "fuck you" that I'm feeling after writing this.
But hey, when you open a new tab it animates.
Maybe you should use the current version for your tests, which supports rounded corners.