I've stayed one night Mario's place while transiting through Vienna.
The check-in was quite late but convenient with the key box. The location of the apartment was great, 4 mins walk to the train station, that had groceries store, pharmacy and cafes.
I found that the communication with the host could've been a bit more personalized. I received quite a few automated messages, some of them not making sense given the information that I've already provided. But generally all good, the host was available and helpful.
The apartment had everything I needed. The kitchen was well equipped and had all the supplies like tea, coffee, salt/sugar, olive oil. There was a washing machine, a dishwasher and a good hair dryer, which were cool to have.
It was a bit noisy in the evening, because there were people singing and screaming next to the train station but at night it was calm.
All in all I'm happy with the stay and would've stayed at Mario's again given the opportunity.