Well, he has some valid points and a load of junk:
If you're seriously in to gaming on a PC rather then console then you're probably better off with Windows and that is likely to remain the case for a long time. Cedega seems to work well for some people, but the people I know that are fanatical gamers would dismiss this as too much effort (read in to that what you will ;) ).
2) Software Support
Umm, this is where he misses the point, and where the average Joe he's talking about probably misses the point of Linux and software freedom too. Being pragmatic about it I can see why some people will want to buy photoshop, but how much non-gaming software that you see for sale in your local store is worth paying money for?
3) Stop assuming people are Linux experts
Face it, Linux is written by geeks and adding user-friendly features is pretty much bottom of their TODO lists. But, there are places for people to look for help - if they can't be bothered searching and reading (hardly need to be a Linux expert to do either of those - waddle over to google and type Mandriva help) then how on earth is anyone meant to help them.
4) Hardware support
Not the fault of Linux developers, perhaps instead of writing FUD he could try to lobby manufacturers to either produce binary blob drivers (will do at a push) or produce true FLOSS drivers. He probably would have more wieght with them than an army of Linux heads.
5) Too many flavours
Someone give this guy a copy of the Cathedral and the Bazaar, he just doesn't get it at the moment.
6) OS zealots
He has a point here, but without people preaching how good Linux and other OS's are how would the masses actually learn of their existance in this MS dominated world.