I have visited this restaurant a couple of times with groups of 3 or more people... although it's not located directly in the city center of Trier, you can easily reach it by foot in approx. 5-10 minutes from the market square. Parking nearby is not so easy, especially in the evening, as many parking spaces are reserved for residents.
The food on the belt is normally quite fresh, but the variety and quality of the fish is unfortunately not always the same (pieces of fish very small or quite greasy etc.) Sometimes certain sorts of fish are missing entirely (e.g. one day no tuna, next time no salmon etc.). If you do the all-you-can eat, they have also a small choice of warm dishes (soup, spring rolls, etc.)
All in all I would prefer some more choices of sushi than having lots of sweets, fruit and yogurt on the belt... the ratio fish-other stuff is unfortunately too much other stuff and not enough fish, especially not in much varieties.
If you want to spend a fun evening with out with some people and having a snack, this place is nice, but Sushi-Lovers who just go there for the food will probably be disappointed. The other Sushi place in Trier (Sushi Trier) actually serves the better food.