It opens to the same angle in a body vs screen sense. Some of you may not be accounting for the fact that the MBA slopes.
In either case, the MBP/MBA/etc angle isn't enough in many situations when I'm genuinely portable and trying to work. Backs of cars are a case in point, but the Air by dint of its low weight is a little easier to prop up/back to make the maximum open angle a little more usable.
However it is definitely less usable in such situations than the Dell D430 or any number of other ultraportables which are actually designed for truly portable use, and not just looking pretty on an executive/PR BS type/designer's desk or on a coffee bar table.