Per has a small but very pleasant apartment with a lot of character. We've stayed there with our family, two kids. The quiet street is conveniently located near a tube station. Östermalm is not as hip and happening as Södermalm, but a good base for exploring every corner of the city. We haven't met Per personally and his communication was brief but sufficient.
If you look for a fancy, super clean place on a lively and hip location, this isn't yours. If you want a cosy, quite place in a more traditional part of town without spending too much, this might be perfect for you.