I stayed at Sarova Panafric for 2 nights in July, and overall really enjoyed the experience. The staff were extremely courteous, the rooms well maintained, and the restaurant had excellent food. I was given a complimentary upgrade after they realized that my room wasn't ready for check-in, which was also much appreciated.
The location is fairly ideal, with it being easy to get a cab to take me either downtown, or towards Junction. The extended driveway means you're removed from street traffic, and also feel extremely safe (given the crime issues in Nairobi).
The lobby and restaurant are definitely the best features of the hotel. Their morning buffet is excellent, and I enjoyed a mix of both continental and local cuisine with excellent variety. Their a-la-carte menu is also pretty solid.
The rooms are spacious, with good air-conditioning, decent wi-fi, good tv channel selection and a really nice shower. The only knock is that the hallways to access your rooms aren't sealed, and tiled with cheap tile, giving the hotel a slightly cheap feel (which it is decidedly not). It has the open hallway look that you expect of a motel, but the facilities and features are definitely top notch.
The only other issue is that I was hoping the hotel would have a gym, but I guess that isn't the norm in Nairobi. The pool area looking beautiful, but it was a bit too cold to swim in July.
Overall, I'd say this is a really good deal if you want a near five-star experience in Nairobi, without having to pay a five-star price. Also, given the alternatives, I'd be hard pressed to find as good a hotel at a comparable price point.