To follow up on my own question, I finally got around to a stay here after COVID wrecked my initial plans in 2020. I'm not going to write a hotel review because it's not a hotel and it is targeting a niche audience. It's a single 2br / 2ba 350 sqm (~3700 sq ft) residence, so it's more like a luxury vacation rental, and it's a unique experience in a former Papal apartment.

The hard product is absolutely amazing. Restored frescoes, elaborate mosaics, great materials and design, unbelievable 26 foot ceilings in the Pope bedroom, etc. The soft product was also excellent given the scope of what they do (i.e. it's not a hotel with 24 hour room or maid service).

While it sounds absurd to say that 4900 EUR / night is a "good value", I feel like you get a lot for your money given the hard product and size of the residence. When I was looking at prices of suites at Hotel de la Ville and Hassler and Hotel de Russie and Six Senses, etc. the same 4900 EUR a night would get you a mid-range not particularly large or distinguished suite. [e.g. Hotel de la Ville wants 4300 / night for 60 sqm "Grand Suite with Terrace" and Six Senses Rome wants 5000 EUR / night for a 75 sqm Corner Suite.]

I'm not going to post a ton of photos showing every room like I normally do because they have very extensive professional photos on their website, but it's very "Instagrammable".