I had big fun reading this thread.
Funny that a person can say a skin should look like some other antivirus interface and then say that another skin looks too much like a certain OS interface... Kind of contradicting...
I'm not judging you here, but just finding it funny to read.
It really doesn't matter. The goal when one creates a skin should not be to try to please the majority, but to create something original or following the creator's particular idea.
If you want to do a skin looking like a certain OS, do it. If you prefer to try something totally new from scratch, do it. You should never create yourself barriers that may diminish your art. Simply follow what YOU personally want to create.
In my opinion, creation of any kind, (music, painting, skin, you name it) should remain total freedom. It's fine if it's inspired by something that already exists, as long as it have something new to reveal, and it's fine if it's totally unknown too.