Stayed at the Apollo for four nights in October with two friends. We were all in the same room, which was a bit of a squash (no space to spread ourselves out), but as we were hardly in, it wasn't too much of a problem.
The room and bathroom were spotlessly clean, the towels were changed every day, and breakfast on the terrace was a great way to start the day. The staff were friendly and helpful, although one was a little too pushy in trying to persuade us to book a taxi to the airport instead of getting the train from Termini.
Other people have mentioned the great location - all the major sites of Rome are within walking distance, the Cavour metro station is five minutes away, and there are lots of buses on the Via Cavour and Via Nationale (the 40 goes all the way to the Vatican). There are loads of local restaurants too - the little square two blocks down has two great ones, both full of locals as well.
Top tip - buy a Roma Card, which gives you free entry into your first two sites (including the Colliseum and Forum), and a discount thereafter, and includes a three day travel pass, which you can use on the metro, buses, trams and trains - excellent value for 20 Euros.