Fiji

Can't help you with Fiji, but if you're open to other alternatives I'd suggest taking a look at Mexico. When we lived in the Pacific Northwest (Vancouver) we looked around for winter escapes too and finally settled on the town of San Miguel de Allende in Central Mexico - the old Silver mining area from Spanish colonial days. The weather there is about as perfect as it gets - mid 80's during the day, high 30's at night, with nothing but sunny days. It's terrific. The laid back ambience of the town is particularly seductive, and there are a variety of interesting day trips that might pique your interest, from the pyramids at Teotihuacan to the Monarch Butterfly Biosphere in the nearby state of Michoacan.
If sea sports are your thing there are numerous places along the Mexican Riviera that surprisingly (to us at least) offer some excellent snorkeling, sailing and SCUBA opportunities. The area around Puerto Vallarta is especially attractive in that regard.
An added attraction is that with the very favorable dollar to the peso exchange rate it's also a pretty cheap winter destination. We spent time down there over the course of 4 winters. It got to be our "go to" winter destination. Might appeal to you too.
Can reach SMA by flying into Mexico City or Leon-Guanajuato and arranging ground transportation from there.
If you're at all interested let me know and I can help sort out the logistics - which are really pretty straightforward.

Pam, are you specifically looking for a scuba diving/snorkeling destination (I've been to a bunch of those), or are you just tossing that out as what you know about Fiji? It's true, the scuba diving there is pretty good...but if you don't dive, what use is that?

There are (literally) countless islands in the South Pacific that one can get to. If you're looking for warm water escapes from the Pacific Northwest during winter (I live in Seattle, so can understand) there are plenty to choose from. Not sure if Fiji makes more sense than a hundred others. What specifically are you looking for?

As pointed out below, lots of Mexico makes an easy (and waaaay less expensive) option of you're simply looking for beach + warm weather (although, as someone who has been all over Mexico, I have to say that anytime someone applies the term "Riviera" to anyplace in Mexico it just makes my skin crawl...).

I think you will get much better info if you can be more specific about what you are looking for (and what you're not).

Point of order, but riviera is a generic term for a coastline...in this case the western coastline of Mexico. It's also a marketing term popularized by economic development entities around the world to advertise their particular tourist areas.

Has anybody been to Fiji and, if so, what were things you found interesting, or enjoyed doing there. If you were disappointed in anything, please share that as well. Thank You!

FYI: you might get travelers that have been by trying the Lonely Planet Forum
https://www.lonelyplanet.com/thorntree/categories/country-forums