I've been knocking round GA for over 20 years now and this 'Wingly' thing doesn't sit right with me. (I'm not making any assumptions about whether this incident falls under Wingly nor am I assuming that the pilot was anything less than qualified and competent).
I expect Wingly is legal but jumping into a light aircraft with someone I don't know and whose qualifications/experience I know nothing of isn't something I make a habit of. The closest I have come is a club flyout where I'm thinking at least this guy/gal is a club member and therefore a relatively 'known' quantity. I did once run through the 'what if I have to take control here' scenario in my mind though.
I have had 'bad vibes' since I first heard of Wingly. Just because something is legal doesnt always mean its a good idea to do it. The people 'promoting' Wingly at a recent aviation event I attended didn't do anything to alay my concerns.