I have confirmed that the centering bug (#3) is fixed both in the latest Orizon and Gen3 firmwares, I had to test in an older ADE to see the bug in action. I have also changed the PNG images to indexed colour, which is what apparently triggers the bug.
Now, this is a report of what I see in my Orizon:
Boo Reader 3.1 (build 1398)
Adobe Reader Mobile 9.2 (build 38311)
1st margin: 5mm/6mm side margins, 1mm on top of the first page
2nd margin: 4mm/5mm side margins, no margin on top
Pagebreak Test: Pagebreak, no top margin after
Justification Test: Correct justification with the "Justify" option enabled or disabled
Centering: Blocks correctly centered and aligned
Auto Margins: All blocks placed on the left.
Long Paragraphs: Spurious pagebreaks after "porttitor nisi. Morbi", "vitae feugiat nisl." With hyphenation enabled, after "enim varius hen-", "blandit rhoncus quam", "felis id urna", "consequat quis", "libero. Aliquam in-".
Empty Elements: All four boxes shown, none with gray background.
Scale Tests: 5cm square -> 5cm; 10em square -> 4cm at 6th font size; 200px square -> 3.1cm (~164 ppi, so 200 real pixels); full height box -> breaks after text, then takes the following page (minus the text height in the first?)
Headers and Footers -> Both bold texts are visible.
PNG Support: 2-bit and 4-bit PNGs have problems, they show spurious hatching in gray areas.
SVG Support: Default text size equivalent to about 26.5 at 6th font size. External SVG appears in in <img> and <object>, but apparently <object> covers everything in its page, including the "As an <object>:" text.
Links Test: Text links work correctly, image links are underlined, but not selectable (key or touchscreen). Multilevel TOC shown flat, all items appear as the same level.
Default Fonts: Default font is customizable, but standard families do not change. "cursive" and "fantasy" look like "serif".
Smallcaps: No smallcaps at all (except in the 3rd paragraph, which is hardcoded), just the normal font.
Spaces: Em-space, thin space, narrow no-break space displayed as question marks, others apparently behave properly. With hyphenation enabled all spaces are supported.
Embedded Fonts: "italic Lobster" looks like normal italic "serif", "bold Lobster" looks actually bolder than normal Lobster.
Ligatures Test: Ligatures used if defined in the font, ‌ breaks the ligatures.
Unicode Coverage: Latin text in normal size (:lang not supported), Armenian and Thai displayed as crossed rectangles (with hyphenation disabled, as question marks). Apparently font substitution happens for characters in Czech, Greek and Russian not included in the font (Verdana, for instance).
Bidirectional Support: Hebrew and Arabic characters not available in default font, with the embedded fonts they are rendered left-to-right and left-aligned; Arabic ligatures used when hyphenation enabled.