I went on a grad trip with 13 of my friends to Villa Ioli. It was a great spot to stay as it was a bit on the countryside, meaning there was a great view.
Everything worked well with the owners manager; Catherine taking care of us. We had 2 cleaning ladies coming for about 2 hours each day, so eventhough 14 guys were staying in the place it was always clean.
There were some minor issues with things such as the wifi, as the radius of it was quite small and at one point stopped working, but Catherine sent somebody to take care of this issue quite quickly.
The villa looks quite similar to the way it was shown on airbnb and is spacious enough to fit the advertised 14 people.
I would say that you definetly need ATV's or a rental car in order to use this villa as it is quite remote and taxi companies usually charge a fortune on Mykonos.
Overall, we had quite a great experience.