For local Vienese food, try Franz. We had the fried steak with potatoes and breaded cutlet with rice along with some soup and salad and every plate was delicious.
For the best Parisian food outside of Paris, try Sarasines Cafe Resto. We stumbled in here by chance one evening and it was amazing. The ambiance is wonderful with three stories, large murals and old fashioned wallpaper, and antiques strewn about including a real park bench taken right off the streets of Paris. My advice would be to order a few things off the menu since the portion sizes are kind of small. Think of this as Parisian bistro food but tapas style. We ordered the mini croque monsieur and some toasties with blue cheese and honey as well as a salad and some beef stew. Excellent.
For amazing Italian food, try Il Sestante. The bruschetta was to die for. It's such an easy thing to make yet sometimes people can really screw it up. The brick oven pizzas were amazing and very affordable. We could have eaten here every day of our trip but alas, we had too much self control. Also, this is the only restaurant we went to that had a high chair. These are rare things indeed in European restaurants.
We had apfelstrudel on three occasions and although it was good everywhere we tried it, the best one we ate was from a super touristy place, the Residenz cafe at the Schonbrunn Palace. The dessert is practically flying out of the oven, that's how popular it is. You can get it with whipped cream or in a kind of cream sauce which are both excellent choices. On every table at the cafe, there's a little booklet explaining in detail how to make an apfelstrudel at home and we nicked one. The Professor is determined to give it a try so I'll keep you posted on how it turns out.
Despite all the cold, we had a wonderful time and are thinking of going back someday. It would definitely have to be springtime though. Or summer. But huddling together against the cold, touching cold noses, and laughing about getting stuck in the snow makes for an unforgettable trip too, I'd say.