Just my opinion, but Mario Kart without online wouldn't be worth a purchase for me. Mario Kart is all about the multiplayer party fun (my friends have spent days playing MK64, and I bought MK:SC and MK: DD both at release so I could play them with my friends. I even hooked up 3 Gamecubes to a LAN and invited over 7 other people just so I could try out DD's LAN play. So far, no one I know has bought a DS besides me, so if MK DS had no online I'd be stuck with just 1p GP and time trials... which bore the heck out of me.
On the topic of whether it should be on-line or on-time, my opinion is that delays are less harmful than reduced functionality. Everyone has the ability to wait longer, but no one can go in and add new features after a game has been released. From Nintendo's perspective, the people who care about multiplayer gaming are more likely to pick up a copy if it has online gaming, and the people who don't give a crap about it will probably still buy it. Also, since this is the first iteration of Mario Kart to have support for online play, it could potentially be a strong system-seller. A small few may decide to give up on the DS because of the delay, but this will be more than made up by people who are drawn in by the promise of online play. So, it's a win-win situation for Nintendo.
Paladin, my advice to you is to either suck it up and wait for Nintendo to release the game when they've finished it, or look elsewhere for your kart-racing fix. There's certainly no shortage, and I know you can't have played all of them. Meanwhile, whining about it accomplishes nothing other than irritating the other members of this forum. (granted, you're entitled to your opinion, but I think at this point you've made your opinion clear.)