Abel Broughton wrote a review of Petzl Zipka 2 Headlamp on May 27, 2011
Overall build quality is good. LED is bright and even, and strobe feature is a true strobe (not the on/off blinking that some headlamps have). This is the same lamp as the Tikka line from Petzl, so you don't have to worry about sacrificing light quality for convenience.
I find that the retractable band makes it much easier to pack and use. I'm not one of those campers who likes wear a headlamp all the time, so its nice to be able to use it as a traditional headlamp or wrap it around my shoulder strap, tent pole, etc.
My only caution is that if you plan on trail running, you should consider a traditional strap. It works well for walking, but jogging or running will cause it to jostle out of place. I've never had any headache issues, having worn it for hours while reading. Overall, it is completely worth the price considering its versatility.