For codes, `pre` tag should be enough, stylesheet just adding some enlightenment. What I'm pointing is that many source code are more than 80 columns wide and that often make you scroll like with PDF. Physical readers are best for content that use aspect-ratio of pocket paper books and as far I can remember coding paper books are more (at least twice) wider and may even suffer that problem (they're often hacks I dislike to split lines.)
To short, Epub per se is not the limiting factor. Vendors must update their hard and soft (even then, things will improve only when everybody has upgraded.) Authors also must take more care to technical contents for that media (some of them convert formulas and codes to image, oooch…)