Even though I picked up this game launch week I've only now had the opportunity to play it. I just beat vision 3-2 (read: the sixth stage) and so far I'm enjoying it greatly. The jumping mechanic it lots of fun. I think it was Jonny who said that in Klonoa enemies are tools (you use them to perform a double jump) instead of simply obstacles. It's a very good way of describing it.
The game isn't as easy as everyone says--there are definitely a few challenging parts. Then again, I haven't lost a life yet due to running out of hearts (although I've lost a few from falling off the stage). I think your average 10 year old would have a hard time with this game.
A couple minor complaints:
1) The English voice-acting is HORRIBLE. Luckily, you can play the game using the original Phantomile gibberish instead. I turned on the English once out of morbid curiosity and was so disgusted I had to restart the stage halfway through just so I could go back to Phantomile.
2) The level design--while somewhat interesting--is annoying because it's not always obvious which way to go. There are many branching paths that lead to collectibles. Unfortunately, it's not clear which path is the main one and which is the branch. I find myself double-backing quite often because I accidentally took the path that leads to the next section.
Overall, very fun game. Definitely worth $30.