Shimogamo is BAR-NONE my favorite Sushi place in the Valley. It's not as inexpensive as some, but the quality of the sushi is truly impressive. I've gone to every sushi place I can in the valley (I live on this side of town) and many places outside of Phoenix (Seattle & San Francisco being the most notable) and I'd place Shimogamo against ANY of them. I'd recommend thier signature roll, as well as many of their sushi pieces, as I've had sushi there that I don't really like anywhere else (quail egg & uni).
Go there. Try it. It's a small intimate place with great service and even better sushi. Reservations probably needed for the weekend and they even have a larger table in the back (a NICE back area) for larger groups.
If there were six stars I'd give them that.