My wife and I spent there 5 days at the beginning of Jan 07. The hotel is rated 4 stars, but in my opinion it couldnt be more than 2. Everything seems great at first glance, but once you go further problems come out. Rooms, corridors, restaurant, everything seems clean, but then you find tons of dust in every single corner. The main restaurant smells of fried fish and potatoes even at breakfast! Food has a really small range of varieties, still, what is served is mostly good.
The beach is really faraway from the hotel; 400m in a straight line, but to get there you need to take a longer road, so it takes about 5-10 mins. Beach wasnt clean at all, plastic bottles and caps.. but maybe they cleanup for summertime.
The personnel is really nice and kind. On the other side, once you make a step out of the hotel there's someone trying to sell you something, so it might be boring.
There's a lovely open swimming pool, but we couldnt use it because it was too cold. There is also a very nice closed and warmed swimming pool and a good thalasso center.
In a overall impression, I may suggest you not to go there and choose a hotel/resort ON the beach. About food/service/etc a lot depends on the managment; Sidi mansour is by now managed by local people. Perhaps you may choose a hotel managed by european personell.