Congratulations! Great exchange.
We are Starwood Prefered guests (Gold thanks to AMEX) and they upgraded our view, even though we exchanged in.
If you can get the Ocean view they are nice, but usually the better ocean views go to the members (if you talk to their sales gruop and express an interest, they may be able to upgrade you as well).
The resort is very nice and fairly new.
Service was a bit shaky on our most recent visit, but we did not worry about it. The sunset can make up for any minor inconvenience.
One word of advice, stock up at costco right near the airport. You can pay for an entire year's membership in one visit (milk at the resort area in $9-10 a gallon, Costco was $5)
The Westin staff is ready for the Costco loads, they have rubbermaid containers on the luggage carts.
The snorkling equipment at costco is cheaper than closer to the resort and good quality. The reef right off of the resort is great, just be careful swimming, the current is very strong.
One of our favorite restaurants was Aloha Mixed plate, try to time it for the sunset it is well worth it.
http://www.alohamixedplate.com/ you have professionals and Tourists sitting next to laborers, it really is a great mix and great experience.
We hiked a bit at Ioa State park, which is really nice:
http://www.hawaiiweb.com/maui/sites_to_see/IaoValleyStatePark.htm
The beds at the resort are great, they have the Westin Heavenly beds.
Assuming for the picture, you have young kids, if you do, there is a neat pirate ship between the 2 Westin resorts. My kids loved it.