I don't really see anyone moving from Tiger to KDE but I generally that a growing Mac marketshare will be good for Linux.
I'm working on one right now. The biggest chink in apple's armor is how it treats it's customers. Massive software is also on the list.(look at your memory usage at bootup and you'll see what I mean)
The main thing I find very easy of a card to play is apple's support. As soon as the new version of their OS comes out, they don't do a whole lot with the previous version.(though to apple's credit their software is very good) It's up to you to shell out more money to get more support. MS isn't much better, but at least they still support their OS's for a few years.(see the recent rollup that just came out for w2k)
The creator of the article hit the nail on the head when he said it's apple's way or the bye-way. It's my contention that apple is more forceful than MS, they just don't have the marketshare to grab attention whenever they flex their muscles.(g4 machines that won't boot OS9)
Being a PPC powermac user, the problem exists without me even having to point it out. "When the intel-mac comes out, I'm not sure sure what I'm doing to do for support."
The easiest answer is linux. Apple doesn't have a whole lot of userbase to lose, but be aware they're losing it too.
Linus uses a linux-only-mac. Naturally he can't be the only one.