I and my wife stayed at Karen Embers guesthouse in Karen, Nairobi for three nights - prior, in-between and after safaris. Our initial booking was for Bush House & Camp, but they turned us away upon arrival despite of our reservation and send us to Karen Embers.
This place is a great choice for moderately priced accommodation in Nairobi - a beautiful colonial house with well kept garden. Fabulous staff and atmosphere, great breakfast and dinner. Fast wi-fi Internet connection directly from the room. The location is in the upscale suburb of Karen, away from hustle and bustle of downtown Nairobi, not that far from Wilson airport (the local fights to the game reserves). We personally could not thing of a better place to stay in Nairobi and would recommend this B&B to anyone who does not need to be in downtown Nairobi.