It looks REALLY nice.
It does look roomier than a Marathon; can't wait for some real-world reviews.
The harness adjuster does seem very low, though. I looked at the pics of the baby rear-facing, and of the seat (side view) installed rear-facing, but I couldn't get a good idea of where the adjuster would be. In the photo of the front view of the seat, it looks very low, though.
As far as 10 inch bottom slots fitting newborns, well, many convertible seats on the market (that are labeled for use at 5+ pounds) have bottom slots of about 10 inches. All the Britax convertibles have bottom slots of 10 inches, The Cosco Alpha Omega Elite's bottom slots are 10.5 inches, the Safety 1st Intera's are 10 inches, and the Safety 1st Enspira's are 9.5 inches.
Some newborns still do fit fine in these seats. Others fit better in smaller convertibles at birth, or infant seats. If straps are slightly above baby's shoulders, as long as the harness fits snug and chest clip is aligned appropriately, it's probably just fine.
http://carseat.org/Technical/tech_update.htm#harnessslot