I guess I owe you all a report from my first visit to Café Kirari this Sunday afternoon. It holds no surprises I guess but someone might find it helpful and enlightening (and hopefully not confusing).
Based on the recommendation from User#8628 above I went to the Kirari Ikebukuro west exit cafe. I had a little bit of difficulties finding the place at first. I wandered off from the West exit just based on vague memories from street view images. After getting lost I made use of the fact that I got a Japanese sim card for this trip and could use an online map to find my way. Then there was no problem. One thing that new visitors to Tokyo should be aware of is that quite a few of any kind of shop or restaurant is frequently not located on the ground floor. So also in this case - the west exit cafe is located on the 6th floor of a building and reached by an elevator. This fact could actually be more convenient for most as no one who sees you get into the elevator can know where you get off. That said, I am not sure what establishments are on the other floors.
The staff at the counter, two young guys, turned out to be very friendly. The first guy I talked to realized that my level of Japanese didn't work for him so he handed me off to his colleague. This other person had a lot of patience with me, but I would have been completely lost if I hadn't read the reviews on for instance this site and Rockitreports. Now when the man tried to make sure that I understood the concept by commenting and pointing to a sheet with images and text explaining the phases of the dating cafe I had no problem confirming that I understood. He also made sure that I understood that a separate negotiation with the girl was included and when I asked whether the women could speak English he said no.
I paid 2100 yen for the membership and an additional 2100 yen for a one-day entrance ticket valid at all the other Kirari shops. He also explained to me that another 2000 yen (I believe it was) was supposed to be paid if you reach an agreement with a woman.
I was really short on time and was about to leave for another appointment, but as I had now paid for a one-day ticket, I made a quick visit to the men's viewing room (let's call it). There were two sections for the women to sit and space in the middle for the men to view them. There was a pretty strong cigarette smell in the room but I also believe there was a refreshening air conditioner present.
I believe there in total to be about thirty seats for the women, but this Sunday afternoon there was only three there. The number of guys was about ten or so. Not much was going on, it seems that the guys were waiting for other options. On a wall there were profile cards for the three women: name, age, measures and some preprinted kanji (checked on non-checked) that I couldn't understand but what I think had to do with what they were interested in doing on a date.
I hesitate to rate the women who were there since that is such a subjective thing, but the three were in the age range 20-26 (at least based on the profile cards). They were average looking but personally I wasn't expecting top models either. While studying the men's viewing room the guy staff showed up to make sure I understood that negotiation with the woman at the shop could not include any monetary exchange. And I confirmed that I understood it. After that I was in a hurry and had to leave the cafe.