Ed,
Yes, the amp rate is the charge rate. Charging Nixx packs at a lower rate is always better for the pack but it does take longer to charge. I never exceed a 1C charge rate and always try and go lower for both Nixx and Lixx packs.
For example; a 2000mah NiMh pack would be charged at a max amp setting of 2amps; 2amps = 1C charge rate. Typically though a 1amp setting is better for the pack; 1amp=1/2C charge rate.
For a brand new pack a forming charge should be used for the first time at 0.2amp or 1/10C charge rate.