This hotel is beautiful - the rooms and facilities (2 small pools, lots of sunbeds etc) are immaculate and the service very personal. Attention to detail (such as hats & beach bag provided in the room) was fantastic.
Great simple breakfast, but otherwise over-priced food. We walked 10 minutes down the beach each evening to Selous bungalows' bar & restaurant, which was much more reasonable and had a more relaxed atmosphere. It was MUCH more expensive to organise trips from here than from Stone Town, so do some serious haggling (on Matemwe beach we were quoted ~8x the price we actually paid from Stone Town to do the dolphin snorkling).
One final thing to note is that swimming is restricted to high tide at Matemwe (and even then we didn't feel comfortable going out more than ~10m), otherwise there are too many sea urchins around. The hotel do provide shoes to protect your feet from them, but apparently they still hurt through the shoes!
Overall though, it is an idyllic spot and luxury hotel - would definitely visit again.
(We stayed for 4 nights, early June 2013, as a couple)