The only reason Top Sushi really prospers is for the same reason many of the eating places around College and St. George prosper: students on a schedule and on a budget.
I admit I fully contribute to this and have been here several times. Just like other restaurants in the area, this isn't the kind of place you go to for a nice dinner with friends. Their food is standard mediocre Toronto sushi restaurant quality -- they've got your basic sushi and most of it is ... all right. Their soup udon dishes are comparable to what I make at home, except the udon noodles aren't chewy enough.
Service is similarly bland. I don't have high expectations of these kinds of sushi restaurants in the first place, but it always irks me when paying by debit or credit card REQUIRES you to go up to the front and pay. Especially around the lunch hour when there are a lot of students ordering take-out, it crowds the cash register area.
Good for an hour's lunch break for a busy student, not for much else.