I used the business lounge in the Roppongi Hills Mori Tower a couple of years ago. I stopped in to use the Wi-Fi to get some work done before meeting someone for dinner nearby.

They have a couple of pairs of Thinkpods (see the Regus website for pictures), though the sides aren't very high and they don't provide much privacy. The person in the adjoining pod was speaking loudly on his phone and was quite distracting. They also have a counter area with stools.

I have one of the free Businessworld Gold memberships. They weren't impolite, but not very welcoming when I presented my card and asked to use the lounge. While working, I was reminded multiple times about the closing time. I wasn't intending to stay until closing, but I felt like they really wanted me to leave sooner rather than later.

For Mori Tower, you have to check in with the building security desk before you can take the elevators up to Regus. My memory isn't clear on this part, but I think I had to provide an ID or my passport before they would let me in.

With free or low-cost Wi-Fi being widely available around town, I probably wouldn't use the lounge again, and I certainly wouldn't go out of my way to use it.