CounterFett was right, these are at Toys R Us, so I picked one up when I was last there. I picked up the Yoshi racer, since I fear that will become the hard to find minifigure as these things go on. I'll have to pick up a Luigi next, as he's my favorite character in the mythos.
This is actually my first K'Nex set ever. They're not quite Legos, but they are certainly compatible. And unlike other block toys that are compatible to Lego, I'm pleasantly pleased by how sturdy and hard the plastic is. It's almost like they were trying to make quality toys here.
A couple things I was weirded out by. The first is that some of the sticker decals are designed to cover multiple blocks, so they're not expecting people to take these apart and construct them in new combinations. There's one sticker designed to go across four blocks. I'm not putting those stickers on until I'm damn sure I'll never take this car apart.
I'm not really sure why they didn't just create a solid block in that shape then. They didn't have a problem doing that with the pullback motor piece. That this is a massive block of plastic that goes in the middle. Of course this means the pullback motor is wicked strong. I pulled it back maybe 3 inches and it went on for like half a minute. (This is perhaps an exaggeration. I did not time it, but it felt like a longish time.)
The second weird thing is that the minifigures are meant to be placed in the car by removing the minifigures legs and placing the torso piece on a peg.
Fortunately the legs are included, so I can have Yoshi minifigure adventures if I so wish. And I do so wish.