It climbs the walls in my pool but not all the way because the fiberglass surface does not provide the traction that plaster will. I suspect that vinyl will be about the same as fiberglass in that respect. the wheels have soft tires that are safe for all pool surfaces according to the literature. Most of the movement of the unit is created by water jets, not traction from the wheels so I don't foresee any problems with a vinyl pool.

As far as robots go, just check out CarlD's horror story about his and the lack of service he got from the factory! Several of the robots that have come out in the past few years just don't seem to work right. Also, although there are models with brushed on the bottom for vinyl pools I think they might create more wear on a liner than other types of cleaners. I am not a big fan of robots.