Fully justified -- there's just no comparison. However, I grok the comment about poor justification -- large whitespace gaps, improper hyphenation.
About a month ago I purchased a new reader -- a Sibrary -- and have been quite pleasantly surprised at just how well it handles justification. It's hyphenation algorithm is superb -- in a month of reading (ca. ten books) I've only seen it make two mistakes.
Another feature that the Sibrary really impresses with is text resizing. It has fourteen levels of resize, from 23 lines per screen / 10-12 words per line all the way up to 6 lines per screen / 3ish words per line. It's only at about the three largest settings that whitespace gaps start becoming noticeable.