I like my 2015 Pure (third owner, low mileage, with heated leather seats and upgraded radio) so much that I picked up a 2015 Brabus (third owner also, even lower mileage). I prefer the styling to that of the newer 2016 on model (no offense to those who own). I figure that the 2015, being the last year, should have most of the bugs out. The previous owner of my 2009 Passion spent more on service than he paid for the car when he bought it new. There seem to be plenty out there with low mileage. Guess no one is doing the Cannonball Run in them. Make for an interesting sub-category though - shortest time coast-to-coast in a Smart.
Try to find a cheap 453... ...you will not be sorry. I had 2 451s that had their own quirks, on my 3rd 453 and haven't looked back since. The added horsepower the turbo provides and the dual clutch 6spd are my main highlights that convinced me to stay with the baby Mercedes!
I'm happy with my 2016 Proxy. The little turbo three-cylinder is a blast. Throttle response is a wee bit disconnected from the power delivery, but one learns to compensate accordingly. It's also not the quietest car in the world, but driving fun more than makes up for any shortcomings. The JBL sound system rocks, material fit and finish is sharp, the DCT shifts are snappy and the car travels perfectly well at highway speeds. It's a hoot to drive.