I've been to Nairobi five times. It's the worst city I've ever been to. Dangerous, totally ugly and just crap. Still if you want your balls squeezed by an HIV infected 15 year old, it's the place for you.
Many places. I stayed at the Stanley several times and drank and ate at Simmers, plus other places. I also stayed with a family that lived in Nairobi. I visited the markets (with a guard of course) and ate at an Ethiopian restaurant which gave me three days of food poisoning.
Utterly shit hell hole.
Been in Mombasa too - the garden of my host's house had monkey on it.
Like most of Africa, the Africans destroy everything.