Recently visited Marakech with a friend. Would recomend spending only 2 full days there as in all honesty, unless you are there for shopping, there is little to do.
Watch out for tourist touts that offer to take you to the medi evil dye pits!
1. They are not really worth the visit (unlike the excelent dye pits in Fez)
2. The touts work in pairs. The first takes you to the dye pit (which you could probably manage with a map) and then introduces you to his "friend" to guide you round the pits. The BOTH expect to be paid, and are prepared to follow you incessently for a very long time if you do not give them enough money.
The main night market is definitely worth a visit, and the food is priced on menues so no hastle there. But the best food we ate there was in a little back street near the museum where a guy was frying fish. Ended going back there twice.