This is the kind of film Saturday matinees were created for. I expect great hordes of new kids are going to become Monster Movie fans over this just like I did as a kid with Godzilla. As evidenced at my screening they do love it.
As a grown up watching it I did have a few issues with it but screw 'em, my over-thinking demographic probably wasn't the primary target. Whenever something dumb happened/was said, the movie seemed to telegraph the message; 'yeah but you're still having a good time revisiting your childhood here so don't try to deny it
'. It's true, I did. A+ from me despite the issues. The 3D is very, very good.
BTW, I didn't see a single commercial for it on TV, only as at theater previews. I wonder if WB underestimated how popular it would be with the older crowd. Heck, besides all the kids Senior Citizens were at my AM screen time!