It depends on the motor, belt, idler wheels, etc. If the table's design allows, helping the platter get going with a manual push removes most of the additional stress from those components. Once the platter's at speed a ring won't hurt them. If anything, the greater inertia will actually reduce demands on the drive train.
Another possible area of concern is whether your TT bearing can support the additional weight without wearing prematurely. Again, it depends on the table.
When I used a ring the most important benefit for me was the improved sinking of resonances out of the vinyl and into the platter, as others described. Flattening of warps was nice but most of my LP's aren't that warped. But they all benefit from a lower sound floor.
Can't use it any longer due to my tonearm, but I'd buy another if I could find one that fit.