I'll start with the positives. Very modern flat right in the historic center close to all the cafes, sites etc. Flat was very quiet during our stay and it has everything you need (hair dryer, yoga mat etc).
Now the negatives. You have to pick up the keys from some place that's a 15 minute hike up a very steep hill AND you have to drop off the keys to the same location. They will not hold your luggage on check out, so you will need to find a luggage rental place or lug your luggage up a very steep hill (not recommended).
The flat also did not have any soap or toilet paper. We had to buy it ourselves and were promised a reimbursement (which we are still waiting on).
Communication is bad...they will respond to you after a few hours even on the day you're supposed to check in.
Due to the complicated check in and check out situation and getting the keys from a far off place, I would not recommend staying here. Trust me, its not worth the hassle.