The good news: It's almost universally cheap by Western Standards unless you go to one of the Exclusive hotels on Nevsky for your meal, and the portions are large. That's it for the good news.
The bad news: Beef stroganof seems to be the only dish. Order any dish that's listed as being made with beef and you'll end up getting something that almost exactly resembles beef stroganor. I swear to God, you could order Sushi and you'd get beef stroganof. Russian beer is pretty crappy, but you can get good Czech and German beers almost everywhere. Russian vodka is obviously wonderful. The coffee is AWFUL!
I've never lost weight on a vacation before in my life. I spent 3 weeks in Eastern Europe and lost 7 pounds. The food's wholesome, edible, well-cooked, but it's BLAND BLAND BLAND.