The Gordon Biersch on Mill is top notch. The location is quite honestly one of the best parts--you're on Mill and 5th and the patio (2nd story) faces the east, southeast, and direct south. You have to go up a flight or two of stairs before you actually enter the restaurant, but once you're almost all the way up, you'll find the bar and open seating to your right and the rest of the dining room to the left. Great views of Tempe, Mill, West 6th, and the distant mountains.
I've had the pleasure of meeting the brewmaster of this Gordon Biersch and he runs a very precise and sanitary operation with the little room he has. The brewery that you can see behind the bar is pretty much it--there aren't any other tanks other than those. Even so, the taps are always flowing.
Food here is good but it is pretty expensive if you're not coming during happy hour. Due to the price, I usually just grab a beer or two with a side of garlic fries. They have the BEST garlic fries on the street. Very satisfying stuff.
I would recommend Gordon Biersch as a lunch or dinner spot, but there are much better places on Mill for late night adventuring.