Seaside was the best place for my girlfriend and I to stay during our short trip to Mykonos. The room was cozy and clean, the views were second to none, and Antonis was the nicest person we met during our whole vacation.
The room itself was perfect: comfortable bed and nice outdoor seating with a view of the ocean. Everything was clean and organized when we arrived and there were even snacks for purchase in our little kitchen. The shower is a little small and has no wall mount but that wasn't a major concern. There are some bugs that fly into the room if you leave the doors open all night so maybe bring some bug spray if that is an issue for you.
Antonis was so accommodating to us during our stay and helped us get the most out of our short stay. He helped us order delivery from a local restaurant and gave us great recommendations for the island.
The location can be a pro or con depending on what you are looking for. It is about at 15 minute drive outside of Mykonos Town so if you plan on touring the island or town during your stay, I recommend renting a car (or an ATV if you are adventurous). We had some construction to deal with while we were there but I'm sure that will be completed by high-season. The beach is very quiet compared to the party beaches of Mykonos and we really liked that.
Overall we loved our stay at Seaside and will definitely be returning on our next trip to the island!