Yum!
Can't think of a reason to buy any other brand of headlamps… Wonderfully constructed, excellent electronics, flood or spot + flood beams, great assortment of goodies in each package (extra o-rings, glow-in-the-dark clips and buttons, and multiple headbands), and of course, the option for warm-tint LEDs (great for outdoor use).
18650 batteries are 3.7V Li-ion rechargeables that are like the stretch-limo version of rechargeable CR123A batteries (aka RCR123A). (14500 batteries are the AA Li-ion equivalent.) They are roughly the same size as 2 CR123A batteries on top of each other. The whole idea of an 18650 is they provide really long runtimes at a voltage that neatly matches the requirements of a modern LED (unlike two RCR123As: ~7.2V). AFAIK, there is no non-rechargeable version of an 18650, so don't expect to find them at a 7-11 on a thru hike. (Some 18650 lights will take two RCR or CR123A batteries in a pinch, which would be a great bonus for the H600.)
The SC80 reminds me of the Gerber Omnivore, a light capable of using AA, AAA, or CR123A batteries (one at a time), the logic being you could salvage whatever you had at home (or could find in a gas station) in an emergency. Now that makes sense for the thru-hiker, but I'm more interested in a headlamp version.