I can't really agree with the statement in point #3: "But neither do you get the extras that are standard with proprietary software: ease of installation, support, documentation, and so on".
I am often drawn to open source solutions because the support tends to be better. Of course I am counting email lists, IRC, and forums as support. I may not get a phone number to call, but I am usually able to get in touch with someone who actually knows the product intimately, as opposed to a call center employee who may or may not be able to go beyond the script that they have been given.
I would not say that installation is always harder with open source software. I would not even say that it is usually harder. Most of the time the competing alternative forces some DRM scheme (licence keys to lose, all sorts mechanisms that break your system and bloat the code at best but tend to introduce bugs) so that the proprietary solution is regularly harder to install and maintain than the open alternative.
In spite of this minor criticism, I like the overall point, which is best summed as: "The critical issue is how thoroughly and thoughtfully the open-source model is applied". Amen to that.