Location: AMAZING! The studio is in one of THE BEST areas of town. It's literally steps from the old town and only a few short blocks from the beautiful Turia garden. There are plenty of shops, cafes and restaurants around. Early in the morning you can get a whiff of the Botanical Garden--literally across the street :) The cafe downstairs has great coffee, btw (a family business).
Kitchen: functional and very well equipped.
Shower: ALL temps and great water stream.
Building: Very quiet. When you do occasionally meet a neighbor, they are super friendly.
Contact with Marina: Excellent. She was very responsive and met me on time.
Mattress: If you are younger than 30, you will no doubt sleep like a baby. If you are over 50, you are likely to wake up with back pains. If the mattress were firmer--and better quality, I'd sure be back--for sure.
Air conditioning: worked well. Some quirky sounds, but they did not bother me.
Marina's studio is an excellent option for a lone-traveler or couple.