The Terminal Hotel in Nairobi City is a great choice for people that want a minimum of comfort in a central location.
Rooms have their own bath and are generally clean.
It is also a very calm location - as long as you request a quiet room that does not neighbour the noisy street or the nearby night club.
Terminal Hotel is not a special place, but if you want to stay in downtown Nairobi and don't want to spend a lot of money, Terminal is a good choice. The rooms are clean and comfortable, the hot water is reliable, and the location is great.
There are plenty of restaurants within easy walking
distance, a huge Nakumatt grocery/department store right across the street, and
it's close to matatu parks and long-distance bus company offices.
Be aware, this place can be quite noisy at night. Downtown Nairobi is just a noisy place to be.
There is an adjoining restaurant/bar which gets loud as the evening wears on, and there are other nighttime resorts of entertainment nearby.
On any given evening, you can expect to hear loud music, people singing karaoke, drinkers shouting and laughing, etc.
This can get annoying, but it's the price you have to pay for staying downtown.
I have stayed at three different hotels in downtown Nairobi, and they were all noisy at night. Terminal is my favorite because it's reliable, clean, and cheap.