Enigma is a nice place, located inside the JW marriott. When i do visit Mumbai annually, my wife and I do make a point of visiting this establishment. The problem with Mumbai is that the city does have a buzz, but there aren't many other decent nightclubs to cater for this atmosphere, which (for the party animal) is a big let down!!
The charges are ok in Enigma for London prices, and drinks are reasonably priced, but be prepared to wait in line (both to get in, and to get served) on busy nights, especially during December and January when the city and especially the Marriott springs to life with locals and NRI's.
If you are lucky enough to stay at JW, then you can queue hop, which saved us a lot of hassle. Juhu does need more clubs like this, because at the moment Enigma has no worthy competetion in the area!
Shamil