As others have noted, this hotel has an air conditioning issue. Actually, we also found it had a plumbing issue--specifically, our room needed a good mixing valve behind its water fixtures. The sink temperature fluctuated rather wildly, and, even more troubling, the shower would swing back and forth from hot to cold with occasional passes through warm. Fortunately, the shower stall was rather large, so dancing out of the way of the blasts at one temperature extreme or the other was easy enough. Still, it made for a rather difficult shower.
Back to the air conditioning issue. We were fortunate enough to be in one of the rooms that had a balcony with a large, sliding glass door. So we could open that and let cool air in from outside. This seems to be part of the idea of not providing air conditioning--that Edinburgh's outside air normally is cool enough to make this an acceptable approach. There are a few problems with this. For one, some rooms don't get enough ventilation to make this work, as noted by others. For another, the hallway outside our door was a sauna. While walking through that may seem a minor inconvenience, it's quite a blast (we're talking about temperatures well into the 80s) and isn't very pleasant, especially when taking laundry down or back up (which is one of the conveniences of this hotel--being able to do laundry).
For us, the biggest problem with this approach was that we both were allergic to something that apparently was in the air when we visited. So we had a choice--either toast in the room or open that sliding glass and suffer with our allergies, tempered only by whatever relief we could get from allergy medications.
Regarding the included breakfast, the food was mediocre at best, but there's a Sainsbury just steps away, and we grabbed things from there and stocked the kitchenette in our room as an alternative. Of course, that's an added cost, but the breakfast really wasn't great and seating was entirely inadequate for the number of people.
With all of that said, the service was good and the hotel itself is quite nice. The location is good, the bed is comfortable, and sitting on the balcony as the sun sets was a lovely way to end a day. They do have work to do on the issues I and others have mentioned, but there are worse choices out there. So I suppose we'd stay there on a future visit to Edinburgh, but the "I suppose we'd stay there" would change to "we'd definitely stay there" if they'd do something about getting air conditioning set up!