I'll bite. I've been to Princeville many times -- growing up in Hawaii, a typical vacation away from Oahu meant going to a neighbor island.
I concur with other posters. Kauai is one of the wettest spots in the world (look up Mt. Waialeale though that is smack in the middle of the island) -- Princeville sits on the northern part of the island -- you are battling the fact that December is on average the rainiest month, and Princeville gets a ton of rain (on average over twice what Poipu does). The rain doesn't bother me, but I know people who won't go during December because you inevitably will end up with a decent amount of rain during your stay.
This plus mfs of over $3k. Can you rent for over that -- sure I think you can for week 52, but it's not an easy rental by a long shot and I don't think you will get much over $3k -- maybe $500/nt? Princeville has a ton of rental property -- both timeshares (though none as nice as the Westin IMHO -- Wyndham has a bunch of stuff up there), condos and single family homes. Look on VRBO, and you can see that you can get ocean front/view condo property for under $400/nt. with a lot of options. Not saying that this is necessarily better, but you can't guarantee any ocean views at the Westin since you will be competing with other owners (I am going to assume that this is not a fixed unit) on timestamp. Look at redweek and you already have two renters trying to rent that week -- they are at $5k and $6k, but I'd bet they'd take less if a buyer offered a lower price.
I think it is a great buy if you are going to use it. I just can't see you making much of a profit given the competition in the area. But all you need is 1 person to rent so maybe you will get lucky.
-ryan