Here's what you need to know:
It's grippy--not smooth. Metals actually provide decent grip under good conditions, but when you're sweaty or the knife is wet, you want G10.
G10 can shrug off huge damage without any visible effect. I've accidentally beaten the heck out of my paramilitary with G10 handles and not only is it not damaged, there is absolutely no visible effect at all even under the closest scrutiny.
It's lightweight and strong. That's enough of an explanation.
It's overpriced. The stuff is awesome, and I pretty much use it exclusively now, but the value is CLEARLY in FRN knives.
By far my favorite....titanium is probably my least favorite because it scuffs so easily and is so expensive. I still have two titanium knives though.