I've done one or two ski mountaineering races each year for the last four years, and I love them. They typically involve about 700m vertical height gain, and I love the extreme physical challenge. It's like the hardest ever erg 10k you've ever done, plus a bit more!
As I live in the UK, it is very difficult to train for these events specifically, and although I am pretty fit from erging/running/triathlon, I have never felt that I've done myself justice in these events.
Having used your SkiErg for the last six months, I managed to knock four minutes off my best time for a 700m vertical race! Most of this improvement I would put down to using your machine 3–4 times weekly for the last six months. I think it is a brilliant fitness machine. It works different muscles than the erg, and I think it is a harder aerobic/V02max type exercise.
Even though it doesn't exactly mimic the ski mountaineering movements (in ski mountaineering there is no double-poling), I think it has been hugely helpful especially with shoulder power.
I have another race at the end of March, so I will be back pounding the SkiErg over the next couple of months again—I'll let you know my result!