Having just returned from a 5 day break in Rome, staying in a Remo (smallest) apartment at the Borgo Pio 2000, I can highly reccommend this accommodation, mainly due to the cost (very competetive compared with Rome hotels), cleanliness (very good), size (really spacious) and location (absolutely excellent) of these apartments.
As we had not been to Rome before, I did a lot of research on Tripadvisor and in the Lonely Planet Guide before booking our accommodation. Before arriving, I was slightly concerned that the apartment might be quite far out of Rome's centre and the main cultural sights, but in fact we walked everywhere from our accommodation (only using the metro to reach the Collussium which took about 10 mins max, and Termini Train Station which took about 15-20 mins max upon arrival and departure) and it turned out to be an excellent location to see all Rome's cultural sights.
NOTE: Before you go, it is worth looking up the Borgo Pio on multimap as the address on the website only states Piazza delle Vaschette, but it is actually on the street called Borgo Vittoro (next to Borgo Pio - where all taxi drivers will know). If you didn't have this line of the address, ir would be difficult to locate. The apartments are only a 10 min walk from Ottoviano metro and it is really easy (and cheaper) to get to them from the airport via the Leonardo di Vinci Express train and then the metro, rather than using a taxi.
I was away with a friend, and the staff at Borgo Pio arranged for 2 twin beds rather than a double in our apartment, and we had a lot of room compared with what you would usually find in a European hotel. It was also nice to have a fridge so we could keep cold drinks / snacks which cut down costs (especially on breakfast). We purchased these items from the local shop (turn right out the of the apartment and Sigma is a 2 min walk on the corner). They have good fresh bread, fruit and veg, cheese and olives.
There are an abundance of restaurants near Ottoviana metro station (just a 10 min walk) including Dino & Toni's which we would highly reccommend - you just sit down and get what you'[re given (about 9 plates altogether of antipasta, pizza and pastas and desserts and a jug of wine). This only cost 50E and we were stuffed! We also took a 10-15 min walk on 2 nights to the area just across the bridge from Castel Saint Angelo - there are lots of boutique shops for shopping in the day (including vintage clothes, bags accessories) and lovely trattatorias for lunch and dinner - look for the hidden gems tucked away off the main streets!
NOTE: If you want to be 'looked after' I would suggest you might be better off staying in a hotel, but if you are happy to do your own thing and use the apartments as a base, the Borgo Pio is perfect. There is an office and the staff are very helpful and friendly, although the opening hours are a little random. But, for example, one evening we had the misfortune to experience our key for the main door snapping in the lock upon coming in from dinner at about 12.30 and we only managed to gain entrance to the building by knocking very loudly and ringing the other apartments until some poor woman woken from her sleep came to let us in! So, don't expect round the clock access to staff!
We were also deliberating whether to buy a Roma Pass which gains you free entrance to up to 2 sights and then discounted entrance to others and free metro, but in the end we didnt and we were glad we didnt! Most of the sights are free, and if you buy your Collussuem ticket at the same time as your ticket for the Palatine, from the Palatine ticket office (just up the road from the Collusseum or the next metro stop along) then you miss the queues anyway, and the metro is only 1E for a 75 min journey. I think, had we bought the Roma Pass, we would have lost money on it.
NOTE: Don't visit St Peters on a Sunday!!!! We made that mistake and waited from 10.30-1.30 when they finally let us in after the Sunday service and an appearance from the Pope. The queues were horrific and actually quite dangerous (a lot of pushing and shoving when the gates finally opened). Apparently we were supposed to gain access at 12.00 so this is obviously not a usual occurance - but be warned!