Have been exploring the options for sushi in the Milwaukee. Here are some places worth mentioning:
Ichiban (downtown): sushi somewhat reminiscent of supermarket sushi (but GOOD supermarket sushi), reasonable prices. Good for a quick sushi fix. Small Japanese grocery store next door.
Restaurant Hama (north Milwaukee): considered by many to be the best Japanese restaurant in the city. I'm not so sure: the sushi is very good, but the other "fusion" dishes on the menu are hit or miss (I've never really liked the salads). The fish entrees are good, but noodle dishes are nothing special. Often busy, especially for dinner. Fairly expensive.
Nanakusa (downtown): I think this restaurant is superior to Hama. Some of the freshest sushi I've ever had, with a huge and exotic selection. Sushi menu changes daily depending on availability. Other items on menu are generally excellent as well; smoked squid salad is terrific, and they even have Kobe beef (which I haven't tried). Interesting ice creams. Good selection of sake, cool decor, surprisingly knowledgeable staff to help navigate the unfamiliar. The only drawback? Small portions, and very expensive!!
Akai Hana (Wilmette): this restaurant is actually in the northern suburbs of Chicago, but I make the drive down occasionally. The sushi is good, and the prices are reasonable; the big sushi trays are an excellent deal. Huge menu of other Japanese dishes. A very good Japanese grocery store next door with quite good selection of condiments, frozen food, snacks, and produce.