This is the perfect location in Athens. Right in the center of everything with 5 minute walks to every great restaurant, museum etc.
Also, I think the venue is fantastic, in terms of views, quality of finishings, etc. The only negative is if you are expecting a large American style hotel room. This is not that. It is a room without any space for you to take your clothing out and put it in a dresser. You will live out of your bags. IMHO that is trivial, and not worth a negative mark.
The other thing is that it is the penthouse, I believe the 8th floor (literally on the roof) of a small office building. The elevator goes to 7, and you need to walk up 15 steps, on a small European set of steps. If you can't do that, don't book this space.
For me, again, the small "downsides" are trivial. The location, quality of the view, AMAZINGLY nice Marika (owner) and Lia (the local manager) and easy back and forth communications, completely outweigh any tiny issues.