Pretty standard drop-off. Every heavily promoted movie has a big opening weekend and then a drop of 50% or more as people turn to the next film.
My kids loved Over the Hedge. Especially the squirrel. I guess every cartoon is going to have an over caffinated squirrel now.
Right now, it's drawing the "I'm not supposed to see this, so I'm going to see it" crowd. That is unlikely to last but, we'll see.
No the standard drop off is 30%, 50% is a bad thing, unless it over performed opening weekend.