Today I was able to play with the new Cosmo in-store. Mini-review:
Good: The 5mm LEDs didn't appear overly blueish, like they do on older Black Diamond lights. Quality plastic body. Gets very dim, and the advertised 55 lumens on high feels about right. Could easily have been made brighter, though. I assume that'll come in future updates to the Spot and Icon models.
Bad: The UI. Turn on, and the Cree turns on at ~50%. Turn off, and the next time it turns on, the 5mm LEDs will be on at ~50%. And so on. Push and hold the button to dim, and again to brighten. Handy: Flashes at min and max so you know it's done ramping. No LED or brightness memory. The XP-E in the one I played with was a bit too blue for my taste (I vastly prefer neutral/warm tints over cool white).
Relative: Like most other headlamps sold for hikers/backpackers in places like REI, it's not waterproof, just rain/splash resistant -- no o-rings, just tight fit on things like the battery compartment cover. Never been an issue for me in practice. Cavers might have a different take.
Probably direct drive like most 3AAA lights.
For ~$30US, it's a good camp/trail light for non-flashaholics. I like it better than Petzl's revamped lineup. I'm not going to get one for myself, though.
