I can only comment on part of your question: one, it's a gorgeous resort, and two, the rest of the island is awesome and you're going to enjoy spending time there.

I did a timeshare presentation there many years ago. It was a different angle though: I was already there on an award stay with regular elite benefits (back when the Ocean Tower had a great lounge), and the timeshare perks were a bunch of free and BOGO activities. There were enough things on the activity list that we wanted to do, so it was a worthwhile 90 minutes. The Hilton timeshare presentation was tasteful (as these things go) and we were able to say no and walk away when it was done.

We've been back a couple times since but not to stay at the Hilton. Did one stay at the Marriott and one in a third-party villa rental. There are a ton of awesome villas in the Waikoloa area....that's the way we're doing it if/when we go back.