I've been using NetBeans 6.5 for some time with Nimbus laf that came with Java 6u10. I have to say I like Nimbus, I am using it and not going to switch back to Metal or Windows. BTW I've always liked the former more, because of good looking toolbar and editor tabs. Anyway, there are two things, for now at least, that annoy me in NetBeans working under Nimbus (I believe these are NetBeans issues) - the colors of editor tabs and their inconsistence and ugly usage of border around editor pane. Look at the picture below.
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I know glitches I've mentioned will not make you scream in the middle of the night sweating, but refining those would please my aesthetic needs :). Of course I am not the only one pointing those issues. Just search for "nimbus tabs" in nbusers@netbeans.org mailing list and you would see polished look does matter to developers.