I stayed at the Marriott on the island of Zamalek in Cairo for work, and was quite pleased. The staff were both professional and friendly and the room comfortable. The room also had a view of the Nile, which was great as it was my first trip to Egypt. I did not sleep well my first night because one of my neighbors kept banging his door -- I called the front desk and that was resolved, however. The business center was also adequate if not totally high tech.
The breakfast buffet was varied and very good. A couple of days I didn't have time to sit down for breakfast and one of the waiters was kind enough to bring me a coffee to go and some fruit.
The location cannot be beat - the area is great to walk around in and has good restaurants.
The former royal palace is a little faded around the edges, which isn't terrible. One mild criticism is that some of the hotel restaurants and bar felt a bit generic (I mean, is Cairo really crying out for a Roy's Country Pub?) but that is largely an issue of personal taste.
One annoyance was that the elevators require you to insert your room card key to get to your floor. This became a problem when I tried to drop off something at a colleague's room in a different part of the hotel and couldn't. This is not an insurmountable problem, however, and I guess on balance it is good that the hotel has strict security procedures in place.
I would not hesitate to recommend the hotel and am considering staying in the Marriott when I bring my parents on a trip to Egypt. It is expensive, however, and I'll have to think carefully if I want to pay these sorts of corporate rates on a pleasure trip.