Here are a few of my personal faves:
BOS:
Legal Seafoods is pretty decent as long as you stick to the seafood and clam chowder. (Before security near the UA check-in area.)
DEN:
Personally, I thought the Wolfgang Puck's Express at DIA (which seemed closer to a a full-service restaurant compared to the one at ORD) is some of the best airport food I've ever had airside. Terminal B, Level 2.
PDX
Rose City Cafe at PDX has lots of Pacific Northwest fare, local microbrews and a pretty decent sushi bar. (Before security near the D/E concourses.) Also, check out the Portland Brewing Co. Pizza Pub in the food court area on the main concourse. They offer, IIRC, ~dozen-plus local micros. Prosit!
SFO
Sanraku Japanese Cuisine, in the food court, offers a limitied selection of sushi packed to-go, but if you have time, order up a nice big bowl of udon. Yum! (Just before gates 68-90, Terminal 3.)