We went twice while staying in Vienna. First time we didn't book so we ate at the counter, with lot of fun. Afterwards we made the required reservation and opted for a non-smokers table, but I suggest you to stay where smoking is allowed which is a better part of the restaurant.
A couple of vegetarians beside us (or maybe he was omnivorous and she was vegetarian, I didn't catch) were disappointed by faux meats because too realistic. He said ironically "Now I need a restaurant where meat tastes like vegetables!". Well, this restaurant is 100% vegan without looking like. That's relaxing, in a way.
Countryside around is nice, after lunch go and take a walk. And remember to ask for homemade cakes not listed on the menu.