From watching field, ground and house crickets mate, I'm almost certain that the cerci play a fairly vital role in ensuring that the male and female align themselves properly. If the male's entirely missing one cerci, the female sometimes seems to 'list' towards the missing side as she climbs aboard, in which case the upwards lunge the male makes when attempting to place his spermatophore more often than not knocks her off entirely and the mating fails.

With the house crickets, the males also seem to use their cerci as part of a visual display when they're in the last phase of their mating dance--they always tuck the ends of their inner wings under the base of their cerci as if to keep them out of the way and show off what a fine length of abdomen they have. I don't know if the long-winged male variants of the field and ground crickets I breed do the same thing. I only get the long-wings occasionally and have never had the luck to see one actually try to mate.

All my crickets will kick back vigorously if they're sitting quietly and trying to mind their own business and their cerci are jostled by another cricket (or just a sneaky bit of tickling by a fine paintbrush) behind them. I'd therefore conclude that they are indeed quite sensitive to touch and appear to be very useful for warning a cricket of invasions of its hindmost personal space! Large nymphs and females resent such jostling the most and are the quickest to retaliate with violent, repeated kicks. Males protest less and are inclined to turn around to see what's going on after only a kick or two.