DO NOT, EVER, ON YOUR LIFE, go into ANY of the bars in Nakasu!
THEY WILL ROB YOU BLIND!
That said, no, I have never gone into the Tennis Club.
Nakasu is great if you are just walking the streets looking at the Korean, Taiwanese, Chinese, Filipino and Malay women standing outside to woo the customers in, and listen to the street musicians (one girl in blue jeans was really cute and had a great voice!) Each bar lets the best looking girls stand outside to attract the men so the sight is something awsome.
But if you take one step inside, do not expect to get out alive without paying 30000yen for a glass of beer or thereabouts. A friend of mine had eighty thousand yen ripped off of him for a bowl of noodles in a Korean joint. Good thing he could afford it.