I'm not sure if the model I bought was a 757, but I bought a PF vacuum a few years ago, and it was the cheapest made POS I ever ran. It has this single-assed small wheel right in the middle of the bottom of the vac which is the "height adjustment" wheel. If you raise it to it's highest position, it still doesn't raise the height of the vacuum, it just digs the wheel deeper into the carpet and pad deeper. You still can't push the darn vac. across the carpet unless you really PUSH hard.
That gets really old after awhile.