Hotel Lord Manaus was disappointing, no hot water, staff not a word of English or helpful, food very poor. This place was mentioned as the best in current edition of Frommer guide to Brazil so it may have deteriorated since then (2008) better hotels are in Ponta Negra not Central Manaus.
Manaus at night is very dark and feels rather threatening Taxis expensive and do not seem to know the city or speak any English. I am sure most people would prefer to stay at ponta Negra and visit Manaus and the opera House etc from there.