OS Gikien makes good stuff, but I'd shy away from a clutch based LSD unless it was strictly a track car. Clutch based LSD's are generally touted as better performers in the twisties. They require more maintenance (fluid changes), and will wear out eventually just like any clutch. Im very happy with a gear type style LSD's.
OS Giken does make some sweet LSD.
When I put the LSD on my Elise, I chose the Quaif one because it was 1/2 the price of the Giken ($1800) but I really wanted the Giken, just could not stomach the price difference.