For noobs, the learning curve for the unity desktop is quite steep. In addition, the fabled customisation options of linux are buried so deep that they give up well before they can reach any place of significance in their understanding.
Drivers will remain an issue as most manufacturers make linux an afterthought.
But, IMHO, to some extent, the plethora of distros, each with their merits and demerits, with their own camps and followers do more to drive away noobs than the actual OS. Choosing a distro leaves one so confused, and the feeling that maybe they made a mistake in choosing the distro when something does not work, drives users to the familiar but oft pirated windows.
Mac X users are a dedicated lot, and having spent the money they do for their machines, they hardly have any option but to learn the OS.
Xandors was an accident and a failure, like it deserved to be.
Letting a new *NIX user know that he is using a new system is fine, but the challenge is not making the learning curve so steep that he gives up or starts loathing using the machine.
Like I mentioned about Zorin, it is UBUNTU based. But made for a newbie. Reduces the learning curve so drastically that getting one to use it is not that difficult.