The Community support is awesome - And there isn't ##windows or ##macosx, or sites like stackoverflow.com in addition to all the articles written by the 90%+ who use OS X or Windows?
Unity is better than ever - Unity being better than ever is an advantage over earlier versions of Ubuntu, not OS X and Windows. What happens if I connect my Dell laptop with an ATI card to a TV to watch a movie?
Beautiful Themes - They are beautiful indeed, but not very polished. OS X and Windows have huge teams whose only job is to make sure that the UI not only looks good, but also is functional and doesn't break down in all sorts of situations.
An enormous free software library - Can I run iTunes on it and sync my iPhone properly? I also want to watch Netflix and Hulu full-screen. Sometimes I like playing that Angry Birds game, is that on there? No? I can't do any of those things? But you say there's a 3D modeler there, as well as something called DDD?
Ubuntu is Free & Open Source - Because all developers and nerds rewrite parts of the kernel the way they work. Also, how does the OS being open source prevent the OS vendor from making huge changes to it? If Canonical introduced a breaking change to your application are you going to fork the OS or fix your app?
Ubuntu is a great OS and arguably the best Linux distro out there, but this article performs feats of logic I have never thought possible.