My husband and I stayed here for 2 nights in early November. The location of the flat is perfect, just a short walk into Grassmarket and about 10/15 minutes to the castle. The flat itself was cosy, clean and comfortable. The building it's in is a bit shabby (not shown in pictures) but once you're inside it's pleasant enough.
The flat had all the amenities you'd need, except a little milk which would've been nice for a cuppa after travelling.
I'd definitely stay again, nice little base for exploring Edinburgh.