Took out the Roloff'd HT last night for a change and noticed one particular benefit of having gears over the usual SS.
Being able to crank a tall gear over level rough ground when going quickly makes for a better natural suspension effect.
With a bigger gear, your legs are providing greater force to the pedals making for a smoother suspension of your body - bit like having a stronger spring, and perhaps slower rebound, rear shock in a full sus.
Apart from that gears are rubbish though.

