I doubt it would be as cohesive as what Apple would do - they are paying legions of top designers to think about every pixel. If it comes super well designed out of the box I appreciate it but I don't care enough to bother tweaking anything. I've tried various plug-ins in Gnome but all pretty amateur compared to what Apple is doing. Of course, I'll stick to Linux as I want to develop in the same environment that my code will be running in production. The other aspects matter far less to me.