Agreed with Diana, generally, more for the scene and possible celeb spotting than for the food. The food is not bad if you can over how "non-Japanese" it is (read: rolls galore & a lot of Americanized Japanese entrees), but still at least slightly overpriced for what it is.
Their soju cocktails, however, can be quite interesting -- but also pretty pricey and I don't recall them having a happy hour.
My full Oct '06 review of GH (+ photos) here:
A meat market for the terminally hip and brain dead. you go to be seen, and if the management doesn't think you're hip enugh, they'll try to put you at the worst table possible. the food is "eh", if overpriced and if you can pay attention to it in all the noise and outrageous design. Prepare to be ripped off if you're not into going to a place for the scene alone.
For good Sushi, go to one of any of the Chowhound fave places ou can find with the search engine.