I'm not too sure that converting those people is actually a good idea. Sure, they'll be able to use the whole thing because I assume that who ever set it up did make sure that all the required options were in place, or taught the user where to find which applications (most desktop / window -managers are quite easy to navigate anyway).
But how are they going to maintain it? Heck, are they going to in the first place?
Although most certainly not perfect Windows updates are pretty simple to apply, most of the work is done behind the scenes. And sure, sometimes things go horribly bad but yah; generally speaking anyone can pretty much do it (and normally it's also being done).
With Linux and FreeBSD not so much in my opinion. For starters: will such an end user try to read into
/usr/ports/UPDATING or do they know about
pkg-updating(8)? Of course I'm only focusing on FreeBSD here but the same can be said about Linux; more than often certain packages provide direct instructions on how to perform an upgrade but most users stop with clicking update in their GUI package manager (if they click that at all).
If you're ignoring all that then it's not as if your system will immediately break down, but it does have the potential to create issues, which could turn into problems over time. And that, together with a possible lack of updates, can lead to security issues.
Which is the main reason why I've always been a little skeptic about these things (for both Linux and FreeBSD): a rogue Unix-like OS/environment can be much more dangerous and damaging than an overrun Windows machine. That's not trying to down talk on Windows because with the proper tools you can also do a lot there as well (PowerShell can be extremely versatile) but even so... Fact still remains that a pristine Windows environment will be able to do a whole lot less than a pristine Unix-like environment.
And that's the part I sometimes worry about when I read stories about end users being put behind full blown Unix environments. Most of them would probably not even realize it if someone else was logged on.