We stayed at Mistral some years ago, and when we decided to celebrate my father's birthday in Hydra, the choice of hotel was pretty easy.
Most rooms at Mistral are as spacious and nicely decorated as seen on their homepage, but a couple of them are rather small and crumpy. (As was the one my sister got on the 2nd floor.) Try to request a spacious room upon booking.
I had a superior double on the first floor which for the occasion served as a 3-bedded room, and that was excellent; still plenty of space and light as it also had 2 windows. My parents superior room on the top floor was also very nice.
It is true that the rooms are not very sound-proof, most noise coming from the corridor through the door. It shouldn't be much of a problem though, as we speak of a small hotel with most clients being adult couples - at least as far as I could judge.
Breakfast was home-made, but not very exciting, if - as was the occasion with the kids- you don't like today's menu, there isn't much of a different choice.
Service was excellent, both the owners and Katerina working in the reception were all very helpful. They arranged for the birthday cake and had it delivered to restaurant we were dining at (Vigla, hope to find them again next year), arranged for manicure at the hotel, and Katerina even ironed my mother's dress herself when she asked where she could have it done!
I see that the estimation of distance from the port vary quite a bit i the reviews on this site, and I will not add any opinion about how many meters it is, but it is a good five minutes walk, that's for sure.

Except from Vigla (new 2007- situated one level up at the turn of the port bay after the bell tower) serving international /asiatic food from the hands of the beautiful true chef wife of the owner, you should try Geitoniko, traditional Greek kitchen, just off the Plateia where Xeri Elia is located.

Coming from Athens with the dolphin we stayed at Hydra for four nights. We paid Eur 100 incl breakfast for a double which is ok.

The rooms at the hotel are nice, although not big (but I think you can find all sizes there, so check in advance - our friends paid the same price for smaller room though). Our room (24) had a small fridge, safe, air-conditioning (ours apparently wasn't working on arrival but was fixed without even asking until the evening) and small TV. The room had a small balcony, just enough for two people standing there but nice for putting the towels there in the evening. Apparently there is also a terrace allocated to some rooms.

The hotel has a nice location, it's 5 minutes walking from harbour, but easily accessible without too many steps. When arriving, you first see the beautiful garden where breakfast is served. It feels great sitting there in the morning or before going out for dinner. Also the lobby is very nicely decorated.

Breakfast was amazing, with different meals changing every days (cake, something salty, hard-boiled egg, jam and white bread, cornflakes is the usualy daily range I think) and you can ask for wrapping to take it with you.

The owners Jenny and Theo are friendly but determined, what I particularly liked is the quick response to emails. Also the other staff was very nice. We could also purchase drinks during the day and sit in the garden; sitting there after going out however not recommended.

For dinner I would recommend "Amalia" and "Christina" for great local food at good value and "Omnilos" for something more stylish and expensive.

What a gem! Hotel Mistral offers everything you expect from a family run hotel. A warm welcome and individuality combined with a courteous service has you relaxed and comfortable from the word go. The extensive homemade breakfast in the beautifully landscaped courtyard provides a perfect start for exploring this stunning island. Only a few minutes walk from the charming, car free, hustle and bustle of Hydra town harbour Hotel Mistral provides the best of both worlds. A quite place for rest and relaxation as well as an ideal starting point to explore the picturesque alleyways, shops, tavernas and beaches of Hydra Island. Thoroughly recommended!

After an overnight stay in Piraeus, Hydra Island was our first extended stay in Greece. We loved the Hotel Mistral and the island. Except for a few municipal vehicles, there are no cars. People walk, bike, or take donkeys. We enjoyed hiking to the monastery, walking to the nearby towns, watching the sunsets, and just sitting at an outdoor cafe at the main harbor and people watching. The Hotel Mistral had an outdoor dining area with lots of plants. It was an oasis on the island. The staff were friendly and helpful. A Greek friend recommended the hotel and island. We're glad we listened to him!