alexbs,
I stayed at the Sheraton at Denaru Island (near Nadi) last Fall and liked it very much. It's a large complex with several different "resorts" within the entire Sheraton resort. I stayed in one of the Villas and thought the accomodations were more than adequate. The staff, extremely friendly. The food, plentiful and diverse in nature (great seafood, obviously).
I stayed for about 7 days and was ready to go by the last day. It had nothing to do with the resort, but rather my own personal preference for what I like to do on holiday/business. Although there are plenty of activities (golf, tennis, scuba, para-sailing, jet skiing, etc.) Fiji (with the Sheraton Resort as my reference) is really a fantastic place to just lay around and do nothing. I'm so used to a heavily urban environment that I literally begin to go nuts after a while of too much peace and quiet!
The weather is typically wonderful...it was very hot and humid in Oct., but I've been hot and humid in worse places!
I only wonder how things are now as a result of all of the unrest? I was there (believe it or not) on business, so I met with a lot of businesspeople and government folks--some of those government folks ended up being held hostage in the recent Coup attempt. There are definite issues between the ethnic Fijian population, and the LARGE Indian population. I have no idea how things are now, given what's happended.
But assuming its safe to travel there, I'd take a look at the Sheraton and see which "resort" fits the budget and needs of the traveler(s). It's closer to the Nadi Int'l Airport, which is the likely entry point for most visitors. Plus, the Sheraton is situated close to several great island "get away" locations, like Beachcombers Resort several miles offshore, which offers a vacation within a vacation.
Also worth mentioning is how affordable Fiji can be once outside of the resort (like most places in the world). Get out of the Sheraton or Fijian and you'll meet some wonderful people who obviously take a lot of pride in their culture(s) and work. Great art, including many wood carvings. Their is also great wooden furniture to be had at some very reasonable prices (assuming you can ship it reasonably). There's junk, too, but a little bit of shopping around and skillful negotiating can yield a treasure trove of keepsakes. You can make your home country Customs Agency very happy if you aren't careful!
Sorry for the long-winded message, but hopefully this gives you some food for thought