Furthermore the Sphero ("facing north") must continually be realigned. One trick drive (as described in the promotional videos) is therefore not really possible.
Tips to get more grip on floor: a balloon over it evert. Then he does not slip so, is quieter and not scratched.
ADDENDUM: The calibration must be adjusted when you move to the "sender" in my experience, just constantly. So nice stop, then make it work!