I can tell a distinct difference between my newer Pfaff and the older ones. No, it is not a lemon. No, there is nothing WRONG with the machine per se. It is just not up to par with the older model. Ho-hum, the honeymoon is over and I went to Babylock instead.
That said: I believe that a sewer/quilter who does not have the older machines as a comparison will notice this as much. If someone test drives a new Pfaff and likes it - by all means, get it.