Today we finally checked out the Muskat I added to Happy Cow a while ago.
There is a daily changing menu as well as a menu featuring small dishes such as breakfast (up to 4pm, not vegan-friendly), salads (i.e. with sunflower seeds and tofu) and snacks as well as beverages (i.e. local juices).
Apparently one soup and main dish per day are vegan. We tried a summer herb soup which was delicious and cost around 3€ and then ordered the dish of the day - a rucola and tomato risotto with red pepper which we really enjoyed and for 6,80€ was still affordable.
The atmosphere inside as well as outside is quite nice - sit by the window and watch the "real" Vienna!
The menu didn't say anything about soy milk for coffee/hot chocolate and there were no desserts - a bit strange for a cafe.
We didn't enjoy the service too much. The owner was more or less friendly but not overwhelmingly welcoming. So we were quite pleased with this place in general until the staff/owner went outside to sit in front of the cafe and smoke a cigarette - and then came back to prepare the food without having washed her hands! Sorry, but both is disgusting to me.
At least Muskat is smoke-free inside - quite an achievement for Vienna/Austria in general.
Cons: service could be improved, could have more vegan options