I was in Dallas this weekend and stopped for lunch in the Deep Ellum neighborhood before heading back to Austin. I went to the restroom before leaving and heard women's voices when I was in the stall (well, it wasn't a stall really, it was a small enclosed room with a full door). My first thought was "Oh shit, I accidentally went into the women's restroom". When I came out a woman was standing there waiting and I kind of gave her the "?" look. She knew what that look meant and said "It's mixed".
The only thing unsettling about the entire experience was when I thought I had gone into the wrong restroom. When I realized it was mixed it was initially sort of weird just because it isn't the norm, but as I was washing my hands it occurred to me that it really wasn't weird at all. There were no urinals and all the toilets were enclosed and the doors went all the way to the floor. The doors locked, of course. There was total privacy. The only interaction was at the sinks/mirrors.
CSB I guess and I know people have concerns about children, etc., but that was my first experience of a mixed restroom in a public place and as an adult it was not a big deal at all.