I've been using an Aquabot for the last four years in my 36' IG vinyl liner pool and love it. It costs more than most of the vacuums out there but it has some advantages that made it worth the cost to me.

-It doesn't rely on the pump so I save money on electricity.
-It does a reasonably good job covering the entire pool.
-It sort of scrubs/brushes the liner rather than just sucking up the loose stuff.

Hope this helps.