This cafeteria-style restaurant came recommended by our local tour guide (who we caught eating there during her lunch break from us). It's about two storeys down from their shop, close to the main square and St. Stephen's. The first storey down contains extra seating and their clean restrooms, so it's a good place to use the bathroom for free!
The food was well-priced for Vienna and it's location (I paid about 12 euro for roast chicken and potatoes, and about 3 euro 70 for a coffee, but it came with a free mug), but not cheap. The food was tasty, and looked fresh and appetizing, but it wasn't anything special. Made to order food had specific foods, or you could pay for a variety of salads and cold food by the size of your plate, or some combination. We ended up returning for a mid-afternoon snack of pastries and coffee. Wifi was free but not very strong.