We spent 5 days in Mirabella Studios and everything went well.
The room was spacious and clean (and also very hot, but there is AC, so problem solved), with a wonderful balcony over the swimming pool and sea.
We didn't try the pool, because there are several beaches near by, and even have a direct access to the sea where you can take a swim in clear blue waters.
If you have any problem or question, Yvonne will promptly help you, and you also have a snack bar where you can have your meals (once again only tried it for one breakfast that was nicely offered by the host, otherwise we were always trying the local restaurants).
If we should travel to Agios Nikolaos area again, we'll probably stay at Mirabella again!