For me, this was really just a commitment in terms of time as the computer response time was quite slow. The questions weren't difficult, although there was a US bias to them, and there was a lot of repitition where the same ones were asked over and over again, so it became a test of memory!
I set myself the challenge of donating 20 trees and I completed that today. I very much doubt that I'll carry on with this as, to be honest, it got a bit boring! Still 1 down, 51 to do.