I used this headlamp all summer fighting fires around the northwest. It is honestly the most efficient and brightest headlamp I have ever used, even though I was very skeptical of the battery pack at the start (I had used a Storm for all my personal purposes the previous few years). The battery pack is so well balanced that you forget about it after a minute or so. I never used it with the chest strap but that's also an option if you don't mind a cord trailing down the side of your head somewhere. Also, I used this headlamp at least an hour every day for over a hundred days, and I changed the batteries ONCE . In fact I doubt I needed to change them as I didn't know about the dimming feature at the time... just hold down the button and the beam dims down until it's minimum brightness, blinks, and then dims back up to full brightness. I was trying to switch to red-light mode with gloves on in smokey conditions and just figured the batteries were dying from the blink and dimness. Also when batteries are dead on other devices (radios, GPS, etc) they still power this thing on a two level of the three level power meter. This thing will drain your AAs to the bottom, and take a while doing so. It'll suck the last juice out of batteries, besides those used for AM radios. When you're trying to save weight and thinking about extra batteries for your headlamp, just think about extra batteries for your GPS because this headlamp will use your old GPS ones (all GPSs run out of juice in 20 hours ish).
It is also the brightest headlamp I've ever used. I used to think my Storm was the king of headlamp brightness. This Icon is just insane. The spot feature is good for at least two hundred feet in all conditions (haven't tried snow yet, mind you). The flood feature is great for smokey conditions that the spot is too bright for.
The only difference between the Polar and regular version is the little insulated battery case. For ten bucks I think I'd go without it because it's not waterproof anyway (though the battery case seals very tightly and never leaked on me).
Get this headlamp.