We recently stayed in Jafferji House for 2 nights and had a mixed experience.
Pros:
Well situated if your goal is to explore Stonetown
Cool, very interesting and unique building, and decor
Breakfast was nice, in a high level semi open air location.
Great spiced coffee.
Rooms are interestingly and well decorated, liked the door locks etc.
Air conditioning is unbelievably good (ice cold room) when it works (see below).
Cons:
Make sure the air con is working. We were here for two nights and the first room we recieved (Massai) the air conditioning did not work (we kind of felt that this was known as we were given the room). As a result the room was damp. We survived the first night with no sleep in swealtering heat, but asked to be changed for the second night. The staff responded well and we were moved without question / complaint which we appreciated. The difference between the two rooms was significant and we were pleased with the second. Honestly I would have checked out and found another hotel had we not been able to move as Massai room was not usable.
Aside from the Air con, we did also feel that the Massai room had not been cleaned at all. Hairs in the bed, mould on the pillow (probably damp related). My wife cleaned the toilet on arrival.
Our second room (Out of Africa) was much better but we still feel the cleaning might have been a bit better in the bathrooms. The shower had dirt in the bathtub for example.
Showerheads in both rooms need some maintenance as they throw water out of the shower (and on to the electric socket in the second room) quite a bit.
In summary if we had the out of Africa room for the entire stay i think i would be giving a fairly good review but given that 50% of our stay was in an unusable room its why i am leaving the rating i am.