Watched this last night, and thought it wasn't too bad. My expectations were low, though. I loved the big monster movies as a little kid, but grew weary of them as I got older; never had an interest in giant robots.
The story could have used some work in areas, there were too many things that didn't make sense. The human parts of the movie were OK, but could have been fleshed out a bit deeper, and not been so obvious. I liked the two scientist characters, and appreciated the goofiness of their genius.
Visuals were fantastic, but I thought the sound was lacking. Sure, there was plenty of deep bass, but it all seemed a bit one-dimensional. Much of the sound design felt noisy rather than layered. It was disappointing compared to the look of the film, and could have been much richer.
Recommended as a rental, Even if it doesn't reach the level of Del Toro's best work, there's enough entertainment value as mindless spectacle.