Well after waiting ages for EBgames to deliver Mario Kart for my DS I've been having a blast with it. So for about a week or so I've been playing the single player version because i didn't have any WiFi here at home and you need a browser to log in at school.
I decided to get a Wireless router because it was only a bit more expensive that the USB thing that Nintendo is selling and it is more usefull. I got it set up with very few problems. My DS kept stealing the IP of my computer, so I fiddled with the router a bit, and all is well.
The game plays online just as good as it does in single player mode. I got my ass kicked a few times but I think I'm getting the hang of it. I would definitly recomend this game to anyone, single player is awesome and multiplayer is just added goodness.
I would have to give Mario Kart DS like 9.7/10 or something stupid high like that.