The Harborfront Marriott is my favorite in the city - maybe because I'm there several times a year I seem to get nice upgrades every second stay or so. The staff are very friendly and the Concierge Lounge has fantastic staff. The location is fantastic, both for being a tourist but also if you have business in the city it's fairly easy to cab/drive/walk pretty much anywhere in the downtown core. This really is one of my favorite Marriott properties of all that I've stayed in in NA.