We were in Edinburgh for the festival, and this flat is in a perfect location: almost all venues are within 15 minutes walk. The flat is definitely a nice place to hang out, with a big room to relax, eat and cook in. The kitchen has all the essentials.
The bedrooms are spacious and have good desks if you need to work. I'd say the mattress on my bed (front room) is towards the end of its acceptable life, and could do with replacing. The shower/loo room is small, and it's a walk-in shower: this is a bad combo, as a lot of the floor ends up wet when the shower gets used.
We had some communication problems: Sam didn't provide check in arrangements ahead of time, and I had to chase this up the night before we traveled. Also, the cleaner Sam used at the end of our stay was told our check out time was 10 am, whereas we were told 11 am.