I test drove one when new, back to back with a MINI Cooper. I got the MINI.
The Lupo felt cheaper, didn't go any better and had nasty, wooden brakes.
And it was dearer out of the box.
Interestingly, if you compare to MINIs they've both held their prices very well.
Not that the residual value would make the Lupo drive any better, or the MINI any better built or more reliable.