I have been to Fiji and absolutely loved it. I compare Fiji to the Caribbean as diving in color vs. black and white. We stayed at Beqa Lagoon Resort and had a great time.
The diving was great, there was a great shark dive, and there are above water activites in the afternoon or you could dive the house reef from shore. If you click on my "photos" link to the left you can see some of my photos. In fact we have booked a return trip to Beqa Lagoon Resort in 2010.
Here is a link to traveler reviews of the resort on tripadvisor.com: Beqa Lagoon Resort (Beqa Island, Fiji) - Hotel Reviews - TripAdvisor.
Australia or Fiji? October 2010 - ScubaBoard