I just ate at the new Planet Sushi the other week (located at 860 Washington Ave in South Beach). It was a great addition to the neighborhood. They have restaurants in Paris and St. Tropez and this is their first U.S. location. The menu is pretty extensive! While it's not the place to go for authentic japanese, it was a good experience. The fish was fresh and the low prices allow you to order a bunch of different things to try. I really was impressed with their spicy tuna! And save room for the dessert sushi if you are a nutella fan.
their website is www.planetsushi.com although I can't figure out how to get the site translated to english - it's currently in french.
I hit up Planet Sushi on Saturday night and it was awful. We ordered two items and left hungry (and made our way to Yakko San for better Japanese). We ordered a tuna tartar to start which was basically cubed tuna and avocado with some sesame seeds on top of rice. Several things were wrong with just this one dish. First, the tuna was cut into quarter-inch cubes, much larger than the small cube or almost ground tuna I've usually had as a tartar. Second, the avocado was not ripe and hard. I tried mashing some pieces to no avail. They were rock hard. There was also no marinade or sauce or anything. It was raw tuna and avocado on top of rice. Lastly, and most importantly, the tuna was not fresh. The cubes ranged in color from a healthy red to a crummy brown (the brown you get when the fish has been exposed to air for too long). It was awful to look at and we picked at the dish for a bit and then left it. We fared better with a Planet Sushi's version of a spring roll with tuna. But after seeing the bare tuna in the tartar dish we couldn't bring ourselves to finish the roll (which, by the way, had the same unripe avocado). Overall it was a bad experience, which is a shame because we really liked the place. We showed the waiter the brown tuna and the unripe avocado and he simply nodded. We asked for the check, paid and left, probably never to return.