Really enjoying it so far. I tried to make some levels in Little Big Planet, but it was too complicated for me to ever try and really figure out. This game, though...you can get as in-depth as you wish. If you want, you can just do a basic track layout, then let the computer auto-finish/auto-populate for you. Very self explanatory.
You can also sit down and place every tree, every power-up, every wall....everything.
Actually laying the track is just like driving the cart. R2 to drive forward (while laying the track), then you can control your elevation, turn left/right. Very simple. Also, tutorials ARE included if you need some help or want to get deeper in the creator.
I made a level called "Alpine Twist" that has some different types of track, a couple devastators and some corkscrew portions of track. Give 'er a download! (please)
Anyway....I'm not generally a fan of racing games. I thought the Split/Second demo was pretty blah...but MNR is just really fun. I even have a good time when I lose online races. I've done maybe 5 XP races and I won one, last place twice and came in about middle the other two. Smiled during all of them, though!
PS - The load times that everyone talks about do exist (I'm starting to get used to them...go figure), HOWEVER....the FIRST time you run the game, the load times are VERY long. They get faster after that first time through though, so don't completely freak out during your first game.