Haven't stayed at Sky City Grand, but the Sky City hotel rooms are pretty serviceable and certainly not cold enough to require a duvet.

That said my preferred hotel order in AKL is Langham -> Crowne Plaza -> Sky City. I generally stay at the CP as work doesn't like to pay Langham rates.

Sky City location is ok, but you get noise sometimes. And I got bored of it and the lack of reward system after ~50 nights over 2005/2006.

The Hilton is probably regarded as the nicest hotel in AKL, and I've never seen a room below $280/night there.