The apartment is stunning, very large and clean, in a beautiful building and a breath-taking terrace. Great kitchen for cooking breakfast with the essentials. A lot of supermarkets on the same street. We went to Santa Caterina Market to get food, but I wouldn't recommend it - it's expensive and unfriendly.
The A/C works really well, although on the last night it went crazy and wouldn't stop beeping... but it cools very well.
Wifi signal isn't strong, but the connection is good and fast enough.
The shower is good and comfortable with enough hot water. Water pressure could be better, but still good. Towels provided were a little rough, and no shower rug/towel.
The Terrace was indeed amazing. It actually isn't private, other neighbors have access to it, so be mindful to lock the door (we got a surprise visit). But it's rare, as I understand.
The location is very good - overlooking the Arc De Triomphe and on the corner of a metro station. However, you do need to walk about 10 minutes to get anywhere special, and the buses aren't comfortable. I wouldn't say it's right at the heart of the city, but close enough.
The only real downside was the mattress, which was sagging in the middle and extremely uncomfortable. Skye said she'd take care of it once we told her- so hopefully this wouldn't be an issue for next guests.
Another issue is that the is construction going on during the weekdays (looks like a big project, so it's going to go on for some time), from around 8 AM onward.. if you are are planning to stay on weekdays and like to nap during the day, this place might not be for you. For us it wasn't an issue.
The place if very very quiet otherwise.
I can't comment about the check-in process since my friend was there to take the keys from the maid (Skye was a out of town). But I did feel it was easy to communicate with Skye.
I'd definitely recommend staying here (given a new mattress).