Really think he's missing the part where laypeople will see the Mac App Store as their main portal for software. Sure us geeks will always know what the best option is, but what about from a common majority consumer's perspective?
In fact, the two conveniences offered by the App Store (visible to users) is ease of finding stuff and security. Security isn't much of an issue with the old model because, historically, there hasn't been many security concerns. If the "finding stuff" benefit goes away too, then the App Store will be completely irrelevant.
I don't know many "consumerish" Mac users who read Mac magazines, Daring Fireball, etc. Hell, I know a lot of more sophisticated Mac users who don't read any Mac related content except when they have problems. Many of the consumer Mac users I know don't pay attention to ads for Mac software either.
On your third point (word of mouth), that one has a lot of validity, assuming that a consumer mac user has a mac nerd or two in his/her circle of friends.
If I look at what most of my consumer Mac friends and acquaintances use, most of their time is spent in Safari, iTunes, iLife, iWork and maybe something like Parallels or VMWare to run "work stuff". A few might install some apps here and there, but few would even know that there was anything outside the App Store that was worthwhile.