It's not too hard, but it's also not forgiving. I think AC/DC is harder.
Houdini is a cradle and aim shooter. Ya gotta post pass and cradle to make shots. It's more technical and not conducive to flailing on the fly.
All the shots are do-able (well, maybe not the milk-can), they just require precision.
It offers nice variety from the Stern multiball games that keep adding balls to the point of exhaustion.