Atomic bindings are NOT flat out of the box. They are 14.2 in the front and 16.2 in the back. They sell 1,2, and 3mm distance plates on the proform for them. So really you are running 1mm of toe lift.
Source - http://www.vikingur.is/media/PDF/ATOMIC_RACE_20102011.pdf page 8!
You're splitting hairs. A 2 mm difference is as close to flat as you'll get in a binding (to my knowledge). Maybe I should have said the Atomic race bindings are the "flattest" rather than "flat", but for all intents and purposes they are flat. The point is that most bindings are around 6 mm to 10 mm higher in the rear, and at 0.4 degrees of ramp with the Atomic that represents a relative 4X reduction in ramp angle compared to most bindings. I used 8 mm for comparison as I just put the ruler to a pair of Fischer FR17s, and there's an 8 mm difference on those.
2mm is 2mm and is VERY noticeable to a strong skier! Flat is flat or zero stand height differential. One degree or 1/2 degree on the frontal plane is also VERY noticeable. I have measured many binding stand height differentials over the years and one year I measured them all! There was a year that a Salomon SC rental binding actually had a negative delta angle which somehow slipped by the product designers attention until after it was too late. Most bindings range from 2mm to 6mm. While this sounds rather inconsequential the skiing reality is very noticeable. Looks and Rossis are now down from 7 or so mm to three to bring the once extreme height down into the normal range of the other manufacturers.
A good skier on hard snow can feel 1mm difference in "delta"! and 1/2 to 1/4 degree in sole cant angle! In the words of Rush Limgaugh, "don't doubt me"!