When we went to Hawaii for our honeymoon last summer we got to see lava rolling down the mountain and it was fucking kick ass awesome. For two geo dorks like us lava is like porn. I wish we could have seen it pouring into the ocean (like it is now) because that would have been almost equivalent to sex. The big island was kinda disappointing otherwise compared to Maui, but the lava totally made it worth it.
If you go to the big island don't stay at the gay german bed and breakfast cuz that guy gave us some kind of stomache bug that really put a damper on our honeymoon. There is also not much on the site to make you think it caters specifically to gay men, but we were the only straight people there. It wasn't a big deal, but we definitely felt a little out of place like we were the straight people that didn't get the clues on the website.
(epilogue: In all fairness I should add the room was beautiful, the property was quite nice, the service was decent and the breakfasts were quite good. I am just pissed that the guy was sick and didn't bother to tell us he had a stomache bug that might be contagious. I really could have done without feeling like hell for the second half of my honeymoon.)