We spent two nights at Fenix for a short break in Rome, and I relied on the guides written here when booking it. You guys didn't let me down! It is a fair distance from the city centre but we used the nearest Metro stop at Bologna to get in and out . As previously mentioned, it is only a 10 minute walk across a safe, quiet neighbourhood.
The hotel hand out a piece of paper with details of the Metro and bus links, but we couldn't figure out which bus number went where, so we stuck to the Metro instead. To get to Fenix from FCO airport, use the 30-minute Leonardo Express (11 euros) to the Termini, then Bologna is just three stops east on Line B. On arrival we used the Left Luggage at the Termini so we could make the best use of our time exploring the city, before retiring to the hotel at the end of the day (for more details on this, I found a good website http://www.roninrome.com with lots of travellers tips in Rome).
We stayed on the third floor overlooking the main road, but the windows are very well insulated and you'd only hear the odd noisy motorbike in the room. In terms of interior quality, ours was fine if a little dark yet everything was clean and in good order. Same goes for the rest of the hotel - it is generally in good condition. It has a nice garden for guest use, too.
Bad points? Well, there is a PC for guests to use which I assumed was free but we were hit with a modest (and surprising) 5 euro charge upon checkout, and while the restaurant served good food in the evening it was totally lacking in atmosphere - they leave the flat screen TV on! There was a mini bar in the room but no coffee or tea making facilities either. Breakfast was very good with a wide choice of food and drink.
Staff were all very friendly and helpful too. We had a 7:30am flight home on the Sunday and they booked us a Mercedes taxi to the airport for 58 euros which wasn't bad value - this included credit card charges and a tip.
Finally, I'd recommend purchasing a ROMA-PASS for your stay in Rome. This gives each person two cards; one for free transport travel (Metro/bus) and the other for two free passes to tourist attractions, both valid for three days from first use. We skipped an almighty queue at the Colosseum using these - at 23 euros per person, it's good value.