Note that the IBM Model M is actually a "membranical" design. Beneath the famous buckling spring is a bit of metal that strikes a contact membrane to close the circuit and register a keypress.
That said, it's nothing like the rubber dome pieces of crap we associate with membrane keyboards; its durability and keyfeel are still legendary. The membranical design may have contributed to its durability by making it less susceptible to dust and dirt.
I still love the patent name for it: "Catastrophically buckling compression column switch and actuator". Still wondering what is catastrophic about it.
That said, it's nothing like the rubber dome pieces of crap we associate with membrane keyboards; its durability and keyfeel are still legendary. The membranical design may have contributed to its durability by making it less susceptible to dust and dirt.