So I've flipped over into bug hunt mode and amongst the various other things I had to do today I decided to tackle some outstanding beasties.
The slowness of loading the slideshow wallpaper was one such problem to tackle. After a couple hours working on it, I managed to reduce the time to build a list of wallpapers by ~97% while also drastically reduce the memory usage. Can you say "low hanging fruit"? :)
What this means, for instance, is that the same 3,200 image and 84 package collection spread out across 91 directories (nested within 4 "top level" directories) went from taking ~14.5 seconds to load on my laptop (which is time spent waiting at log in) to ~0.4s.
Seeing as this process supports both regular image files for wallpapers as well as detecting wallpaper packages while recursing through the directories and avoiding duplicates, that's not too horrible. Probably still space for improvement somewhere in there, but I was feeling pretty good about myself and that little accomplishment ...
... until I read this email from Luboš on kde-core-devel. He wins. :)