Stayed for two weeks at the Sankara during a work trip in December 2011. Very nice, W-inspired hotel, with wireless (spotty at times, but free) service across the property. For business travelers like me who have daily business in town, the hotel is inconvenient due to heavy traffic going from Westlands to town. Also, for longer stays, there is a very little outdoor space, with the exception of the rooftop bar, but that is usually packed with local youngsters smoking hookah.
If, however, you will stick around Westlands (a very nice area), and are just looking to relax at a luxury hotel for a short stay, this would be a good choice. I am going back to Nairobi in January, but will not return to the hotel, due mostly to the traffic of going to town from the hotel (about 45 minutes to 1 hour each way). Also, this time they said they can't match my corporate rate, fair enough.
Service: Very nice at most times, very courteous but spotty. For example, the pool is supposed to be open at 6:00 or 7 00 AM. Numerous times when I went up for a quick swim before my work meetings around 7 00 AM I saw that it was still dirty from the night before (cigarette buds...etc), which I don't mind, but I saw several other guests turning around. One morning I swam with rose pedals from a wedding which had taken place the night before. That was actually a nice experience, but for those that actually want to swim in a clean pool, you'd need to wait a bit longer. Another service experience was regarding the noise level in my room. I was initially given a room immediately below the roofdeck bar. Due to low insulation, most of the noise from the bar trickles down to the room, which woke me up a number of times. I complained 4 or 5 nights about this and nothing happened. The final time I requested to speak to a manager, and then everything improved; she was amazing, and offered me a complementary upgrade to a suite (very nice). But it doesn't change the fact that the service remains average until after you insist on elevating things to management level.
Rooftop pool bar: Very nice in the late afternoon, but is usually packed with local youngsters smoking hookah (not a problem in and out of itself), but makes it a bit inappropriate to hold work gatherings. Otherwise they have very nice cocktails and it is an absolute pleasure to hang out in.
Restaurants: The hotel offers various restaurants and I've tried them all. At best they are mediocre.
Location: Good for hanging out, shopping etc. But not if you have business in town. Westlands to town traffic is usually heavily congested. Also, the westlands roundabout which is right near the hotel is known to a be highly dangerous area (I actually had my iphone stolen from the back of a taxi in the roundabout there). If you will stay at this hotel and will be using a taxi/car to get through the roundabout, make absolutely sure to lock the doors and keep the windows closed.
Rooms: Very nice finishing that is better than African levels. Occasionally there is plumbing problems, but that is to be expected in any hotel in Nairobi.
Tips: The hotel's gift shop has good items (I shopped there myself), and the banana box that is in the Sarit center right near the hotel is also good for souvenirs. There is also a very good Javahouse at the Sarit center. Westgate shopping mall near the hotel also has a good cafe (Art Caffe).