I stayed at Hotel Concorde for two nights and, overall, I had a better experience than some of the harsher reviews. As a two-star hotel, it offers the basic amenities you'd expect—nothing fancy, gets the job done.
I booked a double room, which suited me perfectly for a short stay. The bed was essentially two singles pushed together, but it was comfortable enough. The room had a functioning toilet and shower, a decent amount of space, and a TV. Everything worked as expected. The only annoying thing is the AC can be a bit loud, yoy can somwtimes hear the neighbours, and WiFi can drop, but nothing crazy.
Breakfast was pleasant - simple but satisfying. There were fresh cornettos, juice, water, and the essentials for a start.
As a downside, it would be the area around the hotel. It's close to Termini station, which is very convenient for transport, and very close to usual tourist sites, but the neighbourhood itself is rundown.
All in all, Hotel Concorde is a solid option for a short, budget-friendly stay in Rome.