On the IM site, under research, there should be a link or reference to study published in the American Journal of Occupational Therapy. In that study they compared three groups of boys with ADHD (specific ages, but I forget that right now). The three groups were 1)control group with no intervention, 2)group that played video games (duration, frequency and type of games were not specified in the research article, from my recollection) and 3)a group of boys who participated in IM training.
The IM group and the video game group BOTH showed progress in areas assessed. But the IM group made MORE progress and in more areas than the video game group.
I agree that video game use can improve some skill areas. I think if you can get your son to play DDR and he makes gains, great. The plus for video games is that it is so motivating. We got a Wii console for Christmas. I have no doubt that playing and improving your performance on Wii games (certain sports related games, timing and coordination games) carries over into real life experiences. We just got the purchase of a system approved for our physical rehab dept. I'll be eager to hear how DDR goes for your son!
Good luck!
