SGR
yes it cleans quite well-obviously there is the factor of the differential between the loco rate of travel and the rate at which the cleaning wheels rotate-so i simply run mine in 'slow mode' altho it will still clean in race mode too-albeit lightly
to be honest i do see a bit less in 'first time over' polishing-this is in the way of 'zebra-ing' -but it still works well-so it will take 2-3 swipes instead of 1 (as an overall casual estimation-otoh this also means a bit less wear -perhaps??!
however the benefits are -the loco tracks muc more nicely through points, imho a great deal more smoothly
and does not stall on grades even with wet rails-on my line which does have grades-this is worth it to me having had the loco stall with wet or sap covered rails-it is what prompted me to reverse the grinding direction (which BTW, is entirely and easily reversed without alteration)
as it is nothing more than removing the cowel and the retaining strip and lowering the power block and reversing the motor leads-all of ten mintues max-you should simply see if you like it and works for you