Nothing much to mention. One thing to note is that you will need a car or at least a bycicle, as the nearest grocery shop is in another settlement some 4-6 km away (Võsu) and Merekalda is accommodation only. There is some food available in Käsmu but it is a small village and choice is obviously not abundant. It's worth it to cook yourself at least half the time, at least breakfast, especially if you are an early bird and need to eat before 10 am.
I would not advice the attic room for people with notable accessibility issues - it is the attic, there are steep stairs. However for us, it was not a problem at all.
We only stayed for one night to hike around the Käsmu peninsula, but immediately got the feeling that we should come back and stay longer to relax. Most of this feeling is related to Käsmu in general and the grounds of the apartments - they are large, just on the sea, with direct access to the sea, and a view of the reed, the sea birds and the Käsmu bay. There is no sandy beach, but there is a possibility to rent a boat for example and possibilities to drink your morning coffee right by the sea. There are plenty of sandy beaches around Käsmu peninsula for swimming. We were in their attic room, which was the cheapest one and not too modern, but was still reasonably spacious, clean and had a kitchen corner with a fridge, dishes and water kettle as well as a flat screen TV to watch the football world cup. There is no view to speak of in this room, but we also got to visit the bigger apartments which seemed very comfortable indeed, with a full living room and bedroom, more implements for cooking in the kitchen corner (including a small stove) and some also have a sea view. We were warmly welcomed by the host and got the advice we sought. I also truly recommend Käsmu in general for those who enjoy nature and walks.