I would absolutely recommend a stay at Wendelin's apartment and would gladly stay again myself too. The apartment is in an incredible location, especially if you are new to the city as I was. It is very central and super close to many of the main sites, food spots and cafes that you might want to see in Vienna. The apartment was is really large, comfortable and clean. Wendelin went above and beyond to leave very clear instructions and also recommendations of places to see, eat and drink at (only thing to bear in mind is that the apartment will not have any necessities in and it's a little hard to find regular grocery shops nearby so would be great to add these to the recommendations list too).
Definitely stay here if you want a great experience of Vienna!