I think his main point is that OS X isn't going to offer anything to experienced linux users, in opposition to what O'Reilly implies. I agree with this: most of us have spent time streamlining and configuring linux to work exactly how we like to compute. The reasons O'Reilly cited were obviously coming from people who don't use Linux for it's two major advantages: customization ability, and freedom.
The author here isn't saying that OS X isn't a decent operating system. Perhaps it will even become the next mainstream one, and in fact, I hope it does, but will it pull experienced linux users away from their free software boxes? There's no mainstream reason for that to happen.
Think of it this way: something like 35% of x86 users are *nix users. A much larger percentage are windows users. Considering the shoddiness and cost of windows, it's no wonder people have been trying out linux more than ever. The problem with these people is they want a desktop and system just like the one they "grew up" on. When it doesn't turn out that way (usually after trying Mandrake or some other mainstream dist, none of which, IMHO, are good out-of-the-box systems), they ignorantly critisize linux in general. Those are the kind of user that O'Reilly mostly quoted in his article. Now the thing is, these people make up a majority of of PC users. So is linux best for a majority of PC users? No, I'd have to say it's not. Is OS X? Quite likely.
Not counting OS X, we have 3 major contenders for users' prefered environment: Windows, Linux and previous MacOSs. I believe that for Windows and previous Mac users, the switch would be a no-brainer. Does this make OS X the best operating system for most users? One look at the percentages confirms that. However, linux users have always been the users that had different needs then the mainstream computer user, and always will, I believe. This brings us down to the main point of all this: Mac OS X is not a linux competitor.
I say kudos to OS X, and that I think it's a wonderful idea, and also that the linux community will support it if they know what's good for them, but am I going to switch to it, or would even if it was free? No, for me it would be forfeiting what I consider a perfect operating environment, which I have constructed to fit my needs, and in return, getting something made for mainstream users. I think most experienced linux users share my sentiment that such a switch would be not only pointless, but counter-productive.