Hi there!
Just took the bike for a mix road+gravel ride today at Pulau Ubin.
The bike is really in its most natural state in this type of riding.
I'll probably update this thread about the ride soon.
So its been more than a year now that I've had this bike and its been ridden regularly enough and often at a hard pace w/ fellow riders using road bikes.
No issues with the ride.
There can be some squeeky noise if the folding area is not lubed, but its easily settled with some lube. (maybe once a few months)
No flex that I can feel (though I've never felt it on any bike I've used). (in fact, I think its quite a 'hard' feeling bike with the large diameter seat-tube)
Disclaimer : I'm no bike connoisseur, just a guy who appreciates bikes in all their forms, so if you are looking for a more critical 'princess and the pea' type of appreciation of nuances, I might not be the best guy to feel such things. 
I fold it all the time.
In the house, getting on the train to bring my kids out, or into cars.
Its really not hard to fold (imho).
Wider tires will certainly be better for a more damped ride, though if you ride primarily on pavements, a larger wheeled bike will trade off nimble maneuverability with better rolling.
This is certainly an often overlooked folding bike option and imho as good as any other out there (if not the best for certain type of riding eg. gravel, speed, comfort )