The videos of it so far look great.
The gameplay shouldnt become too complex I believe, it does after all target many very young gamers.
Also even from the brief videos I have seen, there appears to be plenty of fresh ideas , like the Groove-a-tron, people in the crowd were laughing and clapping at this weapon at the Sony gamers day, and innovative gameplay (like fighting the boss upside down).
I'd say it will be a hit.