beside play online
As far as i know thats about the extent of it as of now. More features will probably be released as more developers think of ways to use WiFi
Pretty much exactly what redan said.
You can talk with friends over MPH though. You know, in the lobby?
I Have mario kart ds , is it worth buying it?
Wifi for MK? Yeah, it is. Probably the most fun i had online with my DS.