I joined Idine about two years ago and found it an excellent program -you don't need a separate card, and neither the restaurant nor your guests are aware of the discount. Also, I happened to like some of the restaurants (Gyu-kaku, La Seranata, Zen Grill, Zax etc..).
We haven't dined out this year as much due to our first home purchase, but today I got my revised copy of the list of restaurants and shockingly Valentino is in it, at 10% off at all times.
So if you're thinking of going, join Idine. You'll make back you're fee in one visit.