We really loved the location of this apartment. Everything was just a quick bus ride away but most of the time we decided to just walk. It's about a 20 min walk from the Colosseum and about a 45 min walk to the Vatican. If you have the legs, I definitely recommend walking over bus rides. You get to see so much more of the city. The size of the apartment is perfect for 4 guests. Not too big but definitely not cramped.
The only downsides that we experienced is that the washer/dryer doesn't really work well. It left our clothes moist and not 100% clean. So don't depend on being able to reuse your clothes. The other downside is that the other tenants (probably tourists) leave their trash right outside the main door. This happened everyday that we stayed there. And what's worse, is that we kept getting blamed for it. So don't be surprised if you wake up and see a note on the door telling you to "be more respectful."
Finally, the WiFi was very unreliable. My phone normally picks up WiFi pretty easily but I was never able to stay logged in long enough to actually search something. Luckily, I planned ahead and bought an unlimited sim card at the airport.
Overall I would definitely recommend this apartment to anyone looking to visit Rome. I couldn't imagine having a more perfect location to see all the amazing sights. It was our first family trip to Europe so we can't expect to get everything right. Just plan ahead to avoid these problems.