We stayed at simba lodge naivasha during easter 2013. I think that the hotel was very nice and service there was excellent. Location is also good if you wish to visit e.g. mount longonot or hell's gate.
More on the negative side I must say that the food at the hotel was not good and the spa is not really a spa but rather a couple of cold rooms with massage tables. The rooms do not have mosquito nets above the beds and since the staff opens the windows everytime they visit the rooms, there are a lot of mosquitos in rooms during night time (and naivasha is malaria area).
All in all, I found simba lodge an ok hotel with excellent staff and good location.