We had the pleasure of staying at the Crowne Plaza Nairobi for two nights prior to a lengthy trip in Africa, and have nothing but good things to say about the hotel. The primary purpose of our stay was to help us to get over jetlag, and the Crowne Plaza exceeded in every respect.
The room was clean and bright, but we were able to achieve total darkness when we drew the blinds. The bed is comfortable, and they will provide you with any firmness and size of pillow you want (in case the pillows already in your room are not to your liking).
The coffee bar by the lobby is also bright, with comfortable chairs, and expert baristas. We passed hours reading and people-watching from there. We ate at both Baraza (casual) and Sikia (fancy) restaurants, and both were delicious.
Finally, we arranged for a guide for a day-trip one day. The guide was professional, the price reasonable, and the hotel staff extremely fast and responsive... over e-mail from Canada.
I don't know if we will ever be to Nairobi again, but if we do, we will certainly be returning here.