Excellent and highly recommended.
I visited Rome in August for 3 nights, with wife and 2 kids (11 and 13). I found Giovanni's Sweet Home Colosseo at 310 Cavour as a brand new listing with no reviews yet. But I was impressed by the listing, location, price, and Giovanni's rapid, honest communication, so I booked - and I'm glad I did.
No complaints.
Above all the pros include:
Location: honestly, just yards from must-see sights including: Forum and Colosseum. Convenient for Termini train (and bus) station. Cafes and shops nearby.
Apartment: Clean and well-appointed. 3 comfortable beds (double-upstairs; and nice sofa-beds downstairs - so 2 kids do not need to share same bed). Small but perfectly adequate kitchen and nice bathroom. Plenty of linens, cutlery, crockery etc. Fine for 4 people.
Service: Someone was there to greet us (and offered to arrange transport, had we needed it). And we left out luggage at the office after we checked out, until we left for the airport later. Always v responsive to email and texts.
Good wifi.
Secure-feeling apartment.
Air con seemed fine - even on very hot days. Although we were really on there in the evening, not in the heat of the day.
Value - the price we paid was very good value for such a nice place and location in peak season.

Minor Cons (yes, minor):
- Not much space when both the downstairs sofa-beds are extended - so you pick your way carefully around in a couple of places, not to bang your shin!
- I was surprised by the hotel residency tax (or similar wording) we had to pay in cash upon arrival. Only a few Euro per person per night. I trust it is standard and mandatory in Rom. But I don't remember noticing it in the pricing in the original listing - did I miss that?
- I couldn't turn off the Air-con using the remote.
- Some street noise as it is ground floor (e.g. trash collection etc), and apartment is quite light when the sun comes up, so consider bringing ear plugs and an eye mask if you are a light sleeper (especially with jetlag).

Overall, excellent. Would definitely recommend and would stay there again.