I just purchased a Petzl Myo XP that is the new 2008 model and claims to be 200% brighter than the old model XP. I got a chance to test it today in Howard's Waterfall cave. This thing Rocks. We went with a group of ppl that all had different headlamps, and I'll say that my XP blew them all out of the water, although I think the majority were Wal Mart brands. As we were all walking (about 15 of us) I turned my light off and the overall light in the cave dropped by about 50% even with all the other headlamps going. I would have been about the same brightness in the economy mode.
The "flood" lens is really great. It gives a smooth, even light all around. I usually have to carry a hand held light, however I just put it back in my pack today and forgot about it. Both hands are free now.
The color of the light is very pleasing. I was worried that it would go into the blueish tone but it didn't. It was a very pleasing white color. It will also illuminate very well with the lens flipped down in spot mode. Nothing can hide from this light especially when you hit the BOOST button.
I would like to do a field test between my new Myo XP and the Princeton Apex just to see the visual difference.
I am a beginner at this caving thing so take that into consideration when you read this. However, I know that it makes my old ZOOM look like a wax candle.
There's my review, and I hope it was helpful. Anthony.
P.S. I purchased this at Basegear.com and used their 20% off coupon, and after free shipping, I paid about $65. Not bad.