I've attempted to read technical PDFs on my Kindle. You either need a magnifying glass (if you try to do it a page at a time) or spend the whole time scrolling. Maybe scrolling isn't a big deal on a Kindle Touch, but it's not fun on a standard Kindle.

I don't think this is a question of formats; I think it's a question of "How do we show legible code samples on a 7" screen?".