I'm terribly frustrated by the fact that
1. WordPress doesn't seem to be able to generate thumbnails from large (i.e. 2000 px wide) images.
2. Thumbnail sizes are hardcoded into the WP core itself.
At least, that's the gist of what people seem to be saying when I searched for a simple way to make thumbnails a bigger size.
Both of these seem like they would be an EASY thing for the WP programmers to fix -- add an option that generates thumbnails even if the file is humongous (sure, it uses up a little server time, but that's my time to waste, right? sure, it uses a lot of bandwidth to have large files, but it's my server and my bandwidth to waste, right?), and have there be an easy way to change the default thumbnail sizes (i.e. set a maximum height/width).
I'm somewhat surprised that such a well-developed and otherwise easy-to-use blog system has almost non-existent thumbnail flexibility...
Maybe I'm wrong and it has this ability, but after wasting two days poking around the Codex, I've found nothing which implies as much.