I'm about 35 stars into this now (if it's like SM64, and I've read it is, it'll take around 60 to get to the final boss, and 120 ish for full completion).
I have to say that it is an absolute joy to play, it really is. It has been pretty straightforward so far, it's not mega easy-peasy but it can be rushed through if that's what you want - i hope there are some levels that are more challenging later on, and I'm sure there will be - there have been a coupld of slightly devious bits so far, but rewardingly so - in the way that (as Harrison mentioned) you can see what you have to do but just mess it up a bit, but get that bit further each time.
If you are scared of your inner child-like sense of joy and fun (as Demon Cleaner seems to be), this game is probably too bright and jolly for you - but that's part of why I'm enjoying it so much. Big smile, but I just hope it isn't all over too quickly, and I hope it gets more challenging.