Many FOSS enthusiasts do not realize is that Apple is as, if not more, significant threat than Microsoft in the war for software freedom.
Most of the technical arguments that FOSS evangelists have, fall apart when you are talking about Apple and Mac Os X. Mac Os X has very less, if not none, of the perceived instability of Windows. Default applications bundled with the OS do quite a decent job for many users. And OS being based on BSD itself makes most of the arguments about unix-better-than-windows moot. On top of this, a significant number of well known FOSS folks use Macs. I have seen several photos of FOSS conferences where a large number of the people were using Macs (I am assuming they use Os X. I could be wrong).
So the only argument left to fight about against Apple is the philosophical angle, one that has always been the toughest to get across.
I see this problem becoming bigger as Apple makes further inroads. According to some market reports, they already are a market leader in $1000+ notebooks, and have increased their share to ~10+% in new PC sales in US.
Accordingly, it is very important that FOSS evangelists make sure that their arguments make as much relevance to Macs as to Windows. Stop talking about BSODs, or Viruses, etc. Talk more about the evils of closed source software.