I performed a similar experiment myself and unfortunately I think my results were the same. Though not for the same reasons.

I had an older Core 2 system with a gig of ram that I wanted to set up for my 5 yr old. I wanted something fast on lower end hardware with an easy interface so I decided to try the Netbook edition of Ubuntu.

Install was a breeze and, though a bit clumsy, getting XBMC and a few kids games installed wasn't bad either. Unlike the Download Squad author, I didn't have any problems setting up file sharing either, a quick Google search for a how-to and I was connected to the Movie share on my XP system.

Actually the "Fail" for me came in two forms only one of which was the fault of the Linux distro. First a there were a few little stability problems, nothing major just annoying, solved by closing an app or restarting. The second has to do with it's intended use and is not the fault of Ubuntu but with the overall state of Linux support. Of the many kid friendly game and movie sites frequented by my daughter most do not fully support "alternate" browsers let alone an "alternate" OS. Examples include Disney Channel, Nick Jr, Netflix and though the sites are accessible much of the content fails to load or errors out...

Most of the stability issues went away after the first update but unfortunately the compatibility issues remain. So this is not so much an example of an Ubuntu "Fail" but of the world failing Ubuntu...

If my purpose for this system had been different this would not be a "Fail" but for now I will have to look elsewhere for my kid-friendly PC.