It never bothered me, mostly because that's exactly how my friends and I(and virtually every other kid I knew) were when there were no adults around. Then again, I have never been particularly bothered by cussing.

I heard it. It just didn't phase me in the least. Kids cuss like sailors when adults aren't around. Never found it particularly problematic, as long as it didn't turn mean spirited.
But, back to the actual topic, my Stranger Things project is underway. It's a Flash retheme, with a couple of customizations, new art and some multimedia work. No lower playfield. Rather, I'm using another mechanism to play in the "upside down."

I'd rather see someone else do it anyway. Spooky could handle it well. As much as I like Stern games, I don't think that they do a great job of capturing the feel of a theme in most cases(my opinion, so hold the flamewar). As I said before, I would like to see the game designed as a pseudo-retro 80s sort of thing(which is exactly the route I'm taking on mine). And, I don't think a Stern version would capture that feel.
I'm welcome to being proven wrong, though.

On mine, my approach to the Upside down is UV reactive paint and a dim purple lighting scheme. My thoughts were that the upside down is not another world, but a destroyed version of the "real" world. Thus, thematically, it should be the main playfield. Just my $0.02.

I've just started on my playfield art for my version. I'm hoping to have the overlay printed next month. I'm experimenting with magnet placement right now.

There are new links now. They must have removed the link I posted.