Oh no. The game's as fun as you want it to be. The Story levels are basically just demos showing what you could make. There's millions of user-created levels you can play, and there's a ton that are great. The levels are only difficult if you're trying to go for the trophy for beating each level without dying (in which you're rewarded with a different piece of an outfit for each level completed like this).
I'm not very good at it, so it does make some levels really hard. I've never played with anybody too though so can't comment on the multiplayer part. I do only want to play it every once in a while though, so it does get boring to me fast.