My sister in law got married in Hawaii.
I think for her the main pros were that she loved the area, it gives her an extra reason to go back their on vacations--they have those wedding memories there, and that it was more unique for them. I think she also sort of liked that she could invite extended family (so no one was offended) but know very few would attend.
For her the cons were that she thought most of her co workers she invited would not come, but nearly ALL did and that ran the cost up a lot and also gave the wedding more of a business feel than she wanted (so you cannot count on people not going just because of distance/cost). In her case, she lived and worked in LA and flights from there were pretty cheap at the time--family was mostly in the midwest so it was costlier for us to fly and most skipped.
It was also a con for her that one of her 3 siblings, her twin brother, did not attend. He lived in France at the time and just could not justify the cost and time to fly THAT far and not even be able to also visit friends and his wife's family on the same trip.
As a guest, the con for us is that we felt we "had" to go--and while we wanted to support her, we were young and as a family of four it was a struggle to make it possible. We also felt that if we were paying so much to get there, we should stay and see the area, so we pulled the kids from school for 2 weeks (her wedding was late September).
Another con for me was that the night before was a big dinner and kids were not invited to that (it was just my two and my two nieces). I wanted to stay home with the four kids while the siblings attended the dinner but my sister in law was very hurt that I would skip the dinner and insisted her friend's teen who would be there as well could babysit. I felt very pressured to leave my kids with some random 13 year old we had never met, in a hotel room, and that teen seemed totally overwhelmed with 4 kids in her charge, mine were miserable, etc. If the wedding had been in her hometown, or even where she lived, we would have had more choice of adults or older teens we KNEW and trusted to leave the kids with to attend the event.