One of the factors that one would adapt an OS is it's good User interface. That's why maybe, Mac OS X would win in this area. so why don't we suggest a theme? Let me go first.
Mac OSX Aurora theme (requires Aurora engine) - i don't wanna pretend to be a Mac but for me their theme is just aesthetically pleasing, so i use it.
icon themes - Hydroxygen, oxygen, nuoveXT icon theme
Cairo-dock - this is not a theme but a dock-style launcher, a must. quite stable. theme support. install the latest version, can automatically download themes inside the program
you can google the stuff i mentioned, try it. you can always find themes in GNOME-Look.org