If your'e looking for expensive (but bloomin good) food, head for the Port Olympique area! Otherwise, it's well worth visiting some of the restaraunts away from the main tourist areas (normally only a case of slipping down a side street) - I've found these just as good if not better than some of the 'flashier' restaraunts (there is a local Tapas chain which is excellent but the name escapes me at the moment)
BTW: to get around, use the underground - it's 1 euro per ticket regardless of how long the trip!