As I expected before hitting the vote button, I think it's going to a pretty much 50/50 split or close to it.
I prefer full justified, even though my Sony readers don't hyphenate so there are occasional chunks of white, probably more so on my 5" screen with a larger bold font then there would be on a 6" screen with a normal font. That doesn't bother me at all. The jagged right edge does bother me though.
But everyone's preference is going to be different. I know some who insist on putting a space between paragraphs which I absolutely hate more than left justified. But it's their choice. If a book isn't to your liking, it's really a simple matter to change it to your preferences with great free tools like Calibre and Sigil, or some readers might be able to change margins, font, spacing, justification on the fly.