I checked one out a couple of months ago at REI. I brought a PT Vortec loaded with 4 lithium AA's to compare beams.
The Yukon Extreme wasn't any brighter and the hotspot wasn't round. The problem is that I had to try the light in a brightly lit store, instead of outdoors at night. So it's hard to judge how the beam quality works in real world conditions.
I was hoping the the Yukon would be brighter than what I already had, so I didn't get it. It might be a great light if you need fairly bright with long runtime though.
BTW, the hotspot was affected by the led cutouts in the reflector, diffusion film on the lens might improve the beam.