This is right from the BDX website:
"New for 07' - UP M's and Crossfire is our Diamond Lite Drive system that takes off a true 11 lbs (07'-08') 4lbs (09') of unwanted weight."
The BDX lite gear box looks very simillar to the 05/06 M7 gear box. It's a LOT smaller than the huge mech reverse gear box. your not only saving weight by removing the shift mechanism, but all the reverse pieces INSIDE the gear box (many of which are rotating parts), plus you have to run the billet driveshaft from BDX as well, which saves even more weight.
It's good mod that's not that pricey if you can sell your stock gear box for $300 to $400.
I see no reason to do this mod if you have an 09.