Overall a good stay.
Pros: great location in Rome, extremely close to everything you'd want, and somehow also quiet at night. Hard to pull that off! The apartment is quite large, too, and while the decor is certainly unique in some ways, we found the living room very comfortable. The leather couches were really nice to end a long day of walking on. Kitchen is nice and big, too. Extremely easy check-in and check-out was greatly appreciated, and Andreas is very responsive.
Cons: both beds have different mattresses (we had the whole place to ourselves so we tried both) and we found both to be fairly uncomfortable. Nothing world-ending, of course, and obviously mattress characteristics are pretty subjective. But we've had better night's sleep in Airbnb's and hotels, so at some point an investment in some new ones may really set this apartment apart. The other main thing is the water pressure in the showers, which is quite low. This may be a limitation of the building and out of the host's control, but I find this aspect of a stay to be very important.
We had a great time in Rome, and for the price we found this apartment to be quite good. Improving the mattresses would make it excellent.