Hehe, I know have around 3900m. Marathon isn't that bad when you get used to it (it's such good fun!) I recommend only trying it if you got blue yoshi after the flying section though (you get blue if you land with over 100 points). Challenge mode, now that is tough, I don't have over 3000m in that! Time trial mode gets really hard at the end, trying to be accurate.
I like the fact that it records where you last died, the last time you played that certain level, by putting a little yoshi flag up! By the time ive reached 3000m, i imagine all ill see in the background is flags!! XD
Hehe, it would be cool if they stayed there forever, but the flag only shows the last place you got up to, and when you turn off the game it resets to just after the sky section.
Also, I'm not sure if it's just me, but the game seem a lot nicer visually than I remember from screenshots. It seemed like when you were in the ground section, the top screen would only have empty sky apart from a few clouds. In actual fact there are loads of things to keep it interesting, like big trees and caves. Then again.. it is rather rare to be looking on the top-screen much when you're riding yoshi!
Its bloody hard to keep an eye on both screens! Sometimes you HAVE to keep an eye out for whats going on above you incase those shy guys comes along and shoot cannon balls at you, aswell as the ones that fly down and bug you. Bloody Shy Guys -_-
However, despite how annoying it is, its still a fooking great game!
I'd say it is at the moment my favourite DS game! Even better than Wario and Project Rub. I get around Mario by saying it's a 64 game
Have you unlocked the time attack yet? My top is 2'49''9, and I was impressed with myself!

Time Attack? That sounds cool, and another feature thats unlocked once i reach 3000m... *Mega-Sigh*
I think you get that for beating 300 in score attack.
Hehe, yea i just unlocked TA by getting 308 i think in Score Attack. Baby Luigi! Who would have thought!
My time is very similiar to yours i think. How the hell do you get past those big flower things :S
You just have to shoot them 3 times. You're time can't be close to mine, if you haven't got past the flowers!
Time attack is the hardest mode, I reckon. Well.. actually.. they're all hard in different ways!
Im pretty dam sure about my time. Ill let you know for sure later when i crack it open again
3 times? Damn, thats a lot of fast shooting when yoshi's just strolling up to them, oblivious to the fact he's walking into death!