Double miles come in very handy when you have to take your entire family to the mainland. The generous checked bag allowance (3 pieces) also helps. I also don't mind the complimentary interisland upgrades, since you can board last and jump out first...

I have received the upgrade certificates in the past and have used them each year I have earned them-- I am selective about when/what equipment to use them on. A330's are much nicer than the ex-LTU 767's.