I've had it for a few days now and although my gaming skills have dwindled a bit (40) some of these levels are a pain in the ass. There are 8 worlds and each world has 8 levels (more or less). I have probably have 3-4 hours in it and just did finish world 2. I suppose if someone was really hardcore they could finish it in 2-3 hours but for a casual gamer I think a minimum of 20 hours to finish it is reasonable.
Oh yeah thats 3 or 4 hours in it and I still need to replay some of the levels because I could not find all 3 big stars. Good game. Annoying at times but well made nonetheless.