I completely disagree. I've been using a Model B with xbian for over 6 months now and it plays everything I throw at it flawlessly, even high bitrate 1080p h.264 videos. Sometimes the navigation can have a little latency, or transitions from one category to another (like switching from TV Shows to Movies on the main screen) can stutter or not be smooth, but I partially attribute that to my huge library and the underpowered CPU. The actual video playback itself is always flawless though. I was impressed when I first set it up, I didn't expect it to work as well as it does.
There's this story about an off-duty bridge officer aboard a large US military ship who, groggy after having to get up rather early, called the bridge and requested that the vehicle, some quarter of a million tons of steel, personnel and equipment, be rotated 15 degrees, all so he didn't have to move an inch to get the sun out of his eyes while he drank his coffee.
Maybe whoever wrote that list merely wants to read the Linux Journal forums. Surely we're not pretending as if SELinux doesn't exist and that the NSA hasn't historically contributed to Linux. That would be a foolish thing to do. Of foolishness.
Have you reconsidered a computer career?