The presumed margin of additional safety with this particular product is seems to compare the chronic effects in a traditional seat with those of the new revolutionary seat in static conditions.
But what happens if you have an accident with a baby lying horizontally in the seat? If facing head-forwards, presumably the baby would break its neck. If facing feet-forwards, presumably leg fractures and lower spine trouble would ensue.
The primary function of a car seat should be to protect in a crash - if it doesn't do that it's a bit like:
"Apart from that Mrs. Lincoln, how was the play?" 
I could be missing something, but at the moment I'm not so sure this is a good idea...
All the best,
Andrew.