I agree that the justified text isn't always creating good outcomes. This is particularly true with the margin notes. I like margin notes, but when there's a lot less horizontal space to play with, the justification can cause some really awkward spacing issues.

All of this somewhat undercuts the sentence spacing argument. I think sentence spacing is interesting, and I agree that it should have had more support from css and html, but if your word spaces range from tiny to enormous and vary on each line, it's hard to even really see the sentence spacing.