There’s a reason why most page layout programs considered “Hyphenation and Justification” to be two aspects of the same feature. I strongly agree that you should never use justification without good hyphenation — let alone without any hyphenation at all.
From John Gruber regarding Safari’s Use of Justified Text in Reader
This, my friends, is why the Kobo eReader doesn’t support justification. Without a proper implementation of hyphenation, the text becomes less readable.