Here's hoping they have a piece on Swizzling!
Anybody from the more dynamic languages have any war stories about debugging/maintaining this sort of thing?
I've been lucky never to hit any code where someone did this kind of thing without taking that into consideration, so I can't say how bad it gets when it's screwed up. Used sparingly it can be pretty nice, but you have to be really sure you're not just overcomplicating things for no good reason.
(edit: changed everything. ;-)
Sometimes you need to call stuff which you cannot work around so it is required to patch calls.