Rydges is by Skycity - it is up a hill (Queen St is on a hill) from the waterfront. The city starts to go up pretty much from Custom St so not too many flat places around. The better hotels by the harbour would be Hilton and Westin and the two Mercure's would be at the cheaper end of the market.

I've stayed at the Mercure on Queen St - it's not flash but is clean and a good location.

One option if you were looking for somewhere nice would be the Langham, it's at the top of the hill (cnr Karangahape Rd and Symonds St) but they have a free shuttle to various places in the city which would avoid lots of walking up and down hills.