The nicest hotel close to the Airport is probably the Airport Hilton,
which is very close to the terminal (but not walking distance). Of
course they have a shuttle.

There are many nice hotels downtown. The Hilton Bonaventure is
certainly one of them. Others include the Marrriott Chateau Champlain,
the Hyatt Regency, the Centre Sheraton, and the Loews Vogue. They are
all in convenient locations, but precisely how convenient depends on
exactly where you want to be. These are all large hotels in the
business/shopping district of downtown. There are also a bunch of
small, boutique hotels that have opened recently in the old historic
part of town, if that's your preference.

Ed