There actually was an SVT pre/post dyno with DMD and no other changes awhile back. Showed a gain of 2-3 HP with DMD..
With the price down to $50 (nuts..I paid $90), it may actually be a decent bang for buck (yes sadly $25/HP is not bad for an SVT) mode though it would be nice to see another confirmatory dyno. But for engine saftey its still a must do even if $25/HP is too rich for your blood..