TS I said the same thing! The OP says they'd buy it if it were no heavier than a normal pushchair, but let's say a normal pushchair was 9-10kg, how the hell do you push that upstairs whilst holding your toddler's hand?! Seriously!
Bridget I also suspect you have something to do with this. For one, the YouTube video was added 2 days ago so if you were a normal non-pushchair industry person you'd be highly unlikely to happen across it the day after it was posted. Secondly, you've never posted on MN before - always a good indicator! And thirdly, why get so upetty about it if you have nothing to do with it?
So seeing as we have decided you have something to do with this, send feedback that it needs to be seriously light, say 5-6kg, needs to handle bends and corners on stairs, needs to not be able to fly down the stairs if you slipped, needs to be a one handed push for those like your, er, sister with 2 children, needs a recline, shopping basket, less crappy wheels... feel free to come back for more feedback.
And the pushchair industry is tough so grow a tough skin for your own safety.
Oh and look up the word "procrastinate".