I was on a business trip around Europe that lasted over a weekend, and decided to stay in Rome and play tourist that weekend. Initially I tried to book at a different hotel, but they were full and referred me to the Residenza Arco dei Tolomei. Good thing - this was a great find.
For those looking for a luxury hotel (or even a business traveler hotel) this isn't it. There's no sign out front, no check-in desk, no television with international channels (well maybe CNN), and not a whole lot of staff. What you do get is a very comfortable room with a private bathroom, an EXCELLENT location, and a tasty breakfast. But best of all, as plenty of other reviewers have said already, you get access to Marco and his staff who will answer any question you have about Rome.
Make sure if you stay here to let Marco pick restaurants for you to eat at, and do let him make reservations for you. My first night he sent me to a small place at the end of the street called Enzo, where I experienced Roman-style carbonara sauce for the first time (every time I've eaten this in the past, there was cream in the sauce - not so in Rome.) The second night he sent me to Le Mani in Pasta. Wow! One of the better meals I have ever had - and after I emailed Marco about the meal, he actually called the restaurant for me and got the recipe! (Now if only I could find a local source for Italian truffles...)
One other highlight of the guest house: free Wi-Fi with high-speed Internet. For a business traveler like me who carries a laptop everywhere, you don't know how welcome this was, especially in Europe where Wi-Fi is normally extremely expensive.
I would love to return someday, hopefully with my wife next time.
-Jon