It's very possible that EPUB 3
and Kindle Format 8
will eliminate the necessity of UpSpin's task. But for those who are using current- and older-gen eInk readers and want to continue to get some life out of their devices, UpSpin's tutorial is a yahwehsend. I'm amazed it still hasn't been stickied.
I might try your method of zipping and renaming as well if you tell us exactly how you mean to "reduce the pdf to a series of jpgs" and someone with UpSpin's needs could "strip out unnecessary images." Do you have any screenshots of the results of your doing these things with that sort of book?