Just so you're not just hearing it second hand: yes, we have 10 cars driving around with extender packs already and one 'ultra-leaf', i.e. the 40kWh+extender+3ph charging (all the upgrades we're offering right now). We're installing about one more car per week now and ramping up to full production soon (tm). Over the past few months we've been ironing out lots of bugs and we are pretty confident in the product by now. All that's left is type approval and documentation before we can call it final.
It's going to take a while before we can offer this in the US and Canada. Our insurance expressly excludes US/CA because of liability concerns, so we'd have to offer it uninsured as a DIY at-your-own-risk kit, but even then it might be iffy. Best is probably to find a full producer, installer that licenses our tech or something like that.