It is most certainly a clever idea, and it is reasonably well executed. The controls do take a fair ammount of getting used to, but then it is rare to play a game where it is possible to move so freely in three dimensions.
Once above 20 points or so, it became increasingly difficult to keep track of my tail. when moving around on the "highest" level, it was odd not having somewhere higher to go to, which I often fell foul of.
I occasionally struggled with the pacing of the snake, but not often. Similarly the controls were a little sluggish (pun intended), which means my snake is not that nimble, and more thoughtful. It's a little awkward if you want to play at speed, rather than in a more methodical way.
The fonts are rather mundane, generally speaking, if you would use it in a word document, it's probably not right for a game. Aesthetically a thick modern font would be great, Prototype is a good free one.
The walls are a nice and very useful touch. The way the walls work solves most the problems i would expect in a game like this. The design is good, and it feels close to the original snake, in that it is one's own spacial reasoning ability that provides the challenge.
As I'm always a fan of hi-score tables, I would like to see one implemented, (current hi-score 33)
I'd like to give this game 3.25 stars.