Miku's good, though overhyped.
Food:
Their food is good, though not amazing. Their fish is fresh and I would recommend their sashimi platters. The aburi/oshi isn't as good as other places in Toronto (JaBistro), and so I wouldn't recommend getting it at Miku. They have inventive dishes and appetizers that are fun to try.
Ambiance:
It's a modern and intimate vibe at Miku - perfect for dates. They plate their food really well and it adds to the ambiance of the restaurant. There's lots of seating and the location is near the Harbourfront.
Overall I'd recommend Miku if you want good sashimi, though there's better restaurants in Toronto at the same price point.