I've beaten the a physical version a bunch of times; the first two layers are pretty easy, but the last layer can be a real bitch, although there are a couple of different algorithms you can apply to help you solve the last layer.
That being said, the Google digital version is a completely different animal; it's difficult to control and to get oriented on, and I certainly don't want to admit how much of my workday has been funneled straight down that black hole. Right when I saw the Google doodle this morning I was really hoping that it wouldn't be interactive, as I had a feeling it might be a bit distracting. Luckily, I've been able to break away from its Siren call, and am now using my time much more productively (to read the Boneyard)...