The boat stored next to me used it this spring. A nice glass boat with toe rails, coamings, companionway and a few misc parts. From fresh wood, they applied 3 or 4 coats. That's less work than starting varnish from scratch which needs 7 or more coats initially to work long term around here. The new stuff marketed as Natural Teak is much better than the products I used decades ago on some building projects. That had an another world orange looking finish. The new stuff looks good and will protect the wood.

The folks next to me said they'd put a coat on a year which is the same as varnish. I don't think you need to sand as much or at all but I imagine it would improve and extend the coating. It's more forgiving of application than varnish. Most varnish jobs fail due to lack of initial coats.

I've seen it used successful on some old wooden dinghys on interiors that take a beating from sun with good success.

The one caveat for me would be getting it off. All coatings have to come off sometime. Then it may be more work than varnish which is relatively easy to remove.

Still, if I had little exterior brightwork to protect, I might try it.