Tasty and Authentic Japanese food.
I'm told that two of the tests of a Japanese sushi chef's skill are the quality of rice and tamago (sweet steamed egg ). I'm not a tamago guy, but my wife loved it here. I can attest that the rice is perfectly seasoned, and compliments the firm, fresh and flavorful fish.
We went twice in March of 2007. The offerings included excellent uni (ummm, sea urchin gonads!), deliciously prepared mackerel, sweet shrimp (with tempura-fried heads served on the side), a few rolls made with shiso and umeboshi (personal faves) and lots other selections. The ahi poke was served in a mix of several kinds of seaweed, but with none of the gigartina (red, twiggy seaweed) that the Hawaiians typically use. We still had it both times.
Our non-raw companions enjoyed the soba noodles, which looked handmade; the edamame: large bowls served with what I thought was too much salt, but which others enjoyed; and the crispy-outside/creamy-inside fried tofu served with ponzu sauce and a side of shaved bonito, ground ginger, and chives. I was not crazy about the shumai, but I tend to go straight to the raw bar.
The desserts included home made yaukon (red bean cake) that was earthy and full of flavor, and five flavors of mochi-covered ice cream, which is so chewy-yummy.
The service is great: sitting with the chef/owner at the sushi bar is always a good thing, and our waitress was a cheerful Japanese woman who appreciated our appreciation for other-than-tuna foods.
If you don't want a Japanese dessert, walk around the corner to Saquella Caffe. The Italian desserts, breads, and gelatos are great, as is the cappuccino. It's all served in a very cafe-feeling hip and relaxed setting.
Last tip: As of this writing, there was another sushi place in the same Royal Palm Plaza called ZaZen. It's not terrible, and in fact the waiter at Saquella recommended it over Diamatsu. While we found it to be OK, we would only go back if Diamatsu was closed.