To be honest, I have no idea what you guys are talking about when you talk about "levels." Technically it's not terribly difficult. It just takes practice getting the right sound and voicing out of the little clusters, and the jumps take a fair bit of practice. I'd say the most difficult thing is getting into the right mood for this piece. It should be surprising to the audience AND to the performer. As far as technique goes, I thought it wasn't very difficult, but overall I'd say it really is a fairly difficult piece because of how you need to immerse yourself in it. But then again, I don't think anything is "easy" to play. If i have to though, I guess I could scale it off of a few things.
On a scale of 1-10, 1 being easy, 10 being superbly difficult.
Technical Difficulty: 4.5
Proper Sound/Dynamics: 8
Mentally and Physically getting into the right mood: 8
Take the average that and you get 6.833, round that up and you have a 7/10.
Overall though, the most difficult thing about the piece is really exaggerating everything physically and aurally. It's about the mood, not so much the technique.