We just got home from a cruise on the Fantasy and absolutely loved Lookout Cay, stunningly beautiful beaches, also a totally different feel from Castaway Cay (which we also love). It already looks infinitely better than the early YouTube videos we saw but we can only imagine it will get even more beautiful as the new plantings grow to match the mature areas.
We were a little disappointed that some of the trails, the bike rentals, etc weren’t open yet but that just gives us something new to look forward to when we inevitably go back.
The beach was just wonderful. We are hoping for good weather the day we are there (10-ish days from now).
Most things looked the same for us as the preview pictures, since we were there a scant 4 months after the opening. I don't expect that to really change much - It's going to take years for things to grow in.