It's not going to kill Mario Kart in sales that's for sure.  But Mod Nation Racers has one big mechanic that is simply awesome, the track editor, I booted up the beta today I played for a few minutes and started to make my own track, and it's probably the best custom editor I've ever used.  I made a pretty awesome track within seconds no lie, and I can expand upon it later making hard to see short cuts, make little artistic designs if I want, or let the game populate the track for me which is what I did and it turned out pretty fun.

So far I'd say Mario Kart still has it in the gameplay since I didn't get the feeling of kart variation, the whole drift mechanic, etc.  but the beta keeps kicking me offline and doesn't let you play splitscreen so there are little things I've yet to see. 

Anyone else in the beta played it yet?  What are your feelings so far?

I rather have polished tracks by professional level designers than penis-shaped tracks from everyone and their grandmother.

Funny I made a track thats pretty over the top and as fun to race as some MK tracks and I can make it even better ^_^

you obviously haven't played LBP.

some of these guys are just crazy.

Is the beta on PSN now?

I got my beta code. Sadly my PS3 is in my father's house.

There will be polished tracks.

Along with a HUGE selection of user created tracks. It's like LBP again, in racer form.

OT: I expect it to be greater, quality-wise... But sales, lolol

I am working on a couple of mariocart tracks as we speak:P

I don't think it'll be a Mario Kart killer. What it'll be is the game that the next Mario Kart will ripoff and then Mario fans will consider it the first of its kind. Somehow I keep hearing that the Super Mario Brother Wii is innovating... maybe if Little Big Planet didn't come out first I'd agree. The same thing will happen though, I have a good feeling about it.

Some guys make levels better than professional level designers, you should see it on LBP!