I am using it as an ice axe, so far for icy morning slopes and "piolet panne" (photo) on short steep slopes where my running shoes are slipping a little. I intend to use it for "piolet manche" self belay as well on steeper climbs once the upper elevations here have opened up a bit more.
The sturdiness and reliability are good questions. I was inspired by our good Dr. Jordan's use of them in mountaineering. I have great respect for his technical judgement and his weight/risk tradeoffs. As he has written, "...there is little room for error. Going superultralight requires that you pay careful attention to every detail and evaluate the consequences of each choice you make..." Climbing, even more than hiking, entails the continuous evaluation of risks, such as the distance between pro, the quality of placements, the rockfall potential of a route, etc. Since the manufacturer has not endorsed the use of the Helix as a full mountaineering axe, perhaps because of liability concerns, we must each evaluate the risk of using it.
The way I have evaluated the risk so far is to consider the probability of serious injury or death as a product of probabilities within a set. I have only had to use a self arrest once to save my butt, and that was in an ice climb, so I consider the chances that I will need to arrest at all as being small. (I'm not counting arrests during glissades and rescue situations, which I will avoid with the Helix.) Other possibilities to add to the failure tree are bad runouts, the chance of injury with such a runout, and finally the risk of the axe failing. If the axe has a 10% chance of failing, I still consider the total risk reasonable. The weight savings is so significant that I've been willing to take the additional risk so far.
It would be really nice to know how it actually performs in arrests. I haven't tested it yet, because I suspect that repeated arrests may increase the chance of failure due to fatigue. Has anyone out there done serious arrests with it?