I don't know if you have kids or not, but my DBF and I went (no kids) on a Friday afternoon in March and it was a mob scene. It was kinda overcast and grey out, but still temps in the 70s, but I'm sure the weather had something to do with the number of people inside. We both walked around inside, but EVERYTHING had a 30 minute wait at the very least, including the regular old arcade games. It was at the end of our trip and by then we were so sick of waiting in lines we skipped pretty much everything.
I had added the Water Park and More option to our passes, so it was "free" to get in, and I don't feel it was a big loss. But unless I'm guaranteed that it's deserted in there, I don't think we'll be going back...