I built a similar library on top of YUI called Feature Cue while I was at Yahoo! Sadly it was never open sourced, got rewritten, over-engineered and (as far as I know) faded into obscurity.
I'm glad the Optimizely guys have released their version, because based on our user testing novice users really respond well to this kind of interactive product tour.
I'm glad the Optimizely guys have released their version, because based on our user testing novice users really respond well to this kind of interactive product tour.