Wall textures were one of the first things I did, before I'd decided on the look completely.
From all my testing runs I never fell through the floor so I'd be interested to know where that occurred.
As mentioned in a previous comment, lifts were one of the last additions, changing the speed is easy it's just a case of time limits preventing getting the right balance.
And as for sound effects, I didn't really think about it at all.
I'm happy with how it turned out overall but I think I might revisit it at some point in the new year.