I was in Osaka in June and based on this thread decided that I needed to at least wander through the area for the experience. I went at around 7 PM local time, just before sunset. There were a number of people walking around, and it looked like just about every "restaurant" was open for business.
The map up a couple of posts was very helpful, and I can absolutely confirm that the northern end of the area has the youngest looking girls.
I speak virtually no Japanese (greetings and thank yous is about it) and am clearly foreign, but I was getting nods and waves from at least 75% of the places I walked by.
Was not planning to partake, but there was this long haired young beauty in a soccer outfit waving at me with a big smile and I was hooked. Mama-san gave me a long up and down look, but apparently the girl's enthusiasm convinced her and I was in. A very enjoyable 20 minutes later I was on my way.
This particular establishment appears to have 4 rooms upstairs and they rotate the window girl while the others are busy because when I came back down a different girl was sitting on display.
I would highly recommend at least walking through the area just for the experience, it's like nothing else left in the world today.