This is a slightly contrversial one, but before the accident, if you had asked me my views on Sipadan, this is what I would have said.
Personally I think that Sipadan is not that biologically important. The amount of life their, though incredibly concentrated, is not that much from a regional perspective. I doubt that the reefs of Sipadan are massively important in seeding populations of fish and corals over a wider area.
What Sipadan is, is a biological wonder. A unique habitat, which supports marvellous and amazing variety and density of marine wildlife. The concentration of life on Sipadan makes it truly a wonder of the natural world and more importantly the diving world. Its value is as a showcase, a microcosm of why visiting a coral reef enriches humanity and shows people why coral reefs should be conserved.
I think an interesting parallel is Ngorongoro (spelling?) Crater in Tanzania. Which is another microcosm of concentrated wildlife. Both are natural wonders, but it is the bigger areas, like the Serengetti or the larger reef systems in the Sulu/Celebes Seas, that are more important from a biological perspective.
I guess what I saying is that Sipadan's value is probably more to the diving world, than the natural world. And keeping pristene as a showcase for coral reefs is important. Closing the island to visitors (which I don't think would happen) would be totally counter productive to its role.
Or maybe I am not making any sense at all! 
Alex
