I believe that most testers got the "old" less stiff version of the red 06-07 Mantra since most ski tests were done in Feb. 06 and the in-line change didn't happen until April 06 (I believe). Troutman and/or Squaretail can verify or call me a liar.
Realize it truely is "slightly" stiffened, with more fiberglass (and a tighter weave?) added to the tip and tail of the ski to address some issues that happened during the 05-06 season. Don't make too much out of it. It's not worth dumping the 05-06 model for the 06-07 model unless you're a fashonista.