This weekend I visited restaurant Haštalský dědek. It is new restaurant (I think it has been opened last year) in centre of Prague, in small street near Old Town Square. It has modern interior where man feels good.
You can eat there traditional Czech cuisine for affordable prices. I took great gulash served in small pot with potato pancakes. Only disadvantage this food had what that it was too big when I was not much hungry :-).
Beer was for nice price (22 CZK for lager) and tasted really good (they serve Krušovice beer). They also offer some special beers, however I didn't taste them.
Generally there is nothing to rebuke. I can really recommend you this place if you're looking for good place to eat in centre of Prague.