I saw rhadin's note on another thread (see
here), that expresses a dissatisfaction with full-justification of text in e-books, because it can cause distracting word-spacing, particularly at large font sizes. I thought the subject was worthy of a thread of its own, and maybe even a poll (I've never done one before, so I hope it comes out okay).
The Smashwords style-guide recommends against full-justification, but then says you can try it and see what you prefer. The Amazon instructions for "Building your Book for Kindle", doesn't appear to mention it at all.
When constructing my first e-book I took a look around. While there were many e-books that didn't use fully justified text, it appeared to me that the majority did (not that I did a statistical analysis). I tried out full justification in my own e-book and viewed it in the kindle previewer and my own e-reader and decided that at practical font sizes it didn't look too bad, so I implemented full-justification. I can't say for certain whether my preference for justified text comes from my long history of paper books or not, but to me it just looked neater, somehow easier on the eye.
Of course the ideal would be if it was easy for the reader to choose their own preference (which may well change with the selected font size). Do any e-readers allow this?