I have a definite love/hate relationship with this game. That, of course, means that it's a marvelous puzzle. It's both challenging and highly addictive.
I'd be happier, though, if the placement of the locks and the order in which the pieces are given were genuinely random. I wouldn't mind the strategically-placed, plan-spoiling locks so much if my "opponent" weren't able to hand me the the most useless shapes. The order can't possibly be random when the algorithm shoots me four consecutive 2x2 pieces.
Yes, a good puzzle game needs to be challenging. A good challenge involves frustration. But there is such a thing as stacking the deck too thoroughly.