Not terribly challenging, but a fun and entertaining game with a nice sense of humor.
It is by no means a difficult game, although a few times I found myself scratching my head for a moment before figuring out some of the puzzles. The game has a very...odd, I guess, sense of logic that you'll find yourself laughing at regularly.
The art design is great, especially for a game at this price. Great music and sound effects, and authentic humor (not forced, like so many other lighthearted games).
But the real kicker is the price. It's dirt cheap. Your kids will love it, and so will other non-gamer types (heck, I think even my wife will like it. It's not like I've been able to get her to play Oblivion).
I never thought I'd say it, but this XBox Live Arcade stuff is turning out a hell of a lot better than I would have thought. It makes justifying the cost of the system to my wife a lot easier when there's games on it she can play too!
Buy it. It's fun and cheap. You'll definitely get your money's worth.