I think the biggest issue i have with it is that the kids will literally get together and then play their ds's together.
One of the things I like about my ds, (I am 26 and a gaming geek married to a 27 year old gamer) is that the games usually offer cooperative play, meaning that my ds will send a minigame signal to my husband's ds and then we can play against each other in a mini battle. We haven't tried the full version, and we can only afford one game cartridge, but we really enjoy it when we are waiting to do things. Also on long car rides, one person plays while one person drives. The only thing I dislike is the price of games. It's hard to come up with the money, even for used games, so I like to rent first if I can to make sure it's a worthwhile purchase.
I can understand your hesitance if your dc has an aversion to the end of his technology time, and I want to second what a pp suggested about it being on the weekends. Some of the games are very educational, in a fun and interesting way, and it is very easy to get sucked in.