I gave up a Chinatown chowdown to have lunch with three generations of my family at Crustacean instead. My great-aunt (who was hosting) is a regular there, so we got extra-special service. Even with the service, though, I find it hard to understand why anyone would go there.
It's not that the food is bad, but that it's so... contrived? condescending? commercial? Everything on the menu reads like the result of market research and focus groups. And the whole tone of the restaurant is very snobby (a detailed dress code is prominently posted in the elevator).
Some of the food is tasty. We passed on the crab (which I'd had on a previous visit with my great-aunt and thought was good but not fantastic), but we did get the garlic noodles. Yes, they're yummy, but $9 for about 30 cents worth of ingredients seems a bit excessive. We had a selection of fried appetizers, which were good in a Trader Vic's sort of way, a Vietnamese crepe, which was actually quite good, and prawn salad, which was surprisingly too hot and out of balance -- they only dish I found lacking in execution rather than concept. We also shared two desserts which, as they had on the previous visit, sounded good but were fairly tasteless. Didn't see the bill, but whatever it was, it was too much.
In short: if someone else insists and is picking up the tab, go ahead -- the food is edible. But I can't imagine any circumstances under which I would spend my hard-earned money at Crustacean. There's better Vietnamese food in the city at half the price and none of the snobbery, and there are other options for Vietnamese fusion/fine dining as well.