I didn't realize that Bromptons no longer have the free swinging rear frame. I have one such older Brompton (1999 model, owned from new) and I love its folding action - it literally takes less than a second and I do it as second nature whenever I park the bike. The Vello doesn't even come close, especially as that rear fold is virtually useless without folding the front too. The only time the free swinging is a hassle is when trying to do maintenance - if you want to stand it upside down you need a bungee cord to hold it in place (not an issue with the Vello). It has never been a problem while riding, over well over 10,000km, though it can lift a little on very uneven ground, and I'd certainly not want to try any stunts with it! I rarely ride it now, though, partly because it is old and worn (and the parts are really expensive to replace), but mainly because the Vello is so much better against the wind and up hills. I miss the gears a lot (my Brompton is one of the old 5 gear Sturmey Archer models) and the fact that the Brompton can consequently go way faster when conditions are right. On the whole, though, the Vello rides a little better, is not perceptibly heavier, and that motor really helps.
[MENTION=517620]Vellonaut[/MENTION], I'm impressed that you keep it in Bike+ mode: that's too much effort for me, as the max power available on that mode is only about 150w and the overall effort involved is greater than it would be for an equivalent manual bike, albeit spread much more evenly. You're right, on that setting it is really useless on more than a very gentle slope. Mine mostly stays in ebike mode, which (with a bit of judicious back pedalling down hills and when braking) can keep it going for about 50km and provides about 225w of power, which is significantly more comfortable up hills. The turbo mode gives the full 250w, but eats battery way too fast and makes it too easy on the flat, requiring virtually no effort up to 25kph. I may experiment with other settings again some time but, as you say, the app is clunky and, more to the point, bug ridden to the point it can render the motor inoperable for several minutes if you use it. Definitely one to set at the start of the journey and leave it. It has also stopped recording the distance travelled some of the time, so even that potentially useful feature is worse than useless. I find it very disappointing that a perfectly decent and very clever bit of engineering can be let down by such an awful bit of software, and that Zehus does not seem to be committed to developing or properly supporting it.