The comments at this page might help:
http://www.factson.net/738/brainetics-reviewIn reading up on Brainetics, it became apparent to me that Brainetics marketers may be posting comments to prop up their product. For instance, on one page I found multiple verbatim "Is Brainetics a Scam?" posts that resembled little infomercials for the product.
Brainetics appears to be a collection of math shortcuts. These certainly won't improve overall math understanding or mastery. But for a kid who needs practice with calculation, it could help slightly, I suppose, especially if it increased confidence. I don't see Brainetics as likely to increase long-term interest or proficiency in math.
ETA: The name reminds me of the fictional malady "boneitis" from Futurama ("My only regret... is that I have... boneitis! {gasp}").