Actuation force ratings are misleading because the stiffness you perceive is a product of the entire travel of the switch, and not just how stiff it is at the point of actuation. Black Cherry switches actuate at 60g, Blue Cherry switches are also 60g at their stiffest point, despite being much easier to type on than Black switches. Many find the buckling spring, whose peak/actuation force is 65-70g, to be less tiring than the Black Cherry, and so on.
Oh, hate to be anal, but a "membrane keyboard" doesn't necessarily imply rubber domes. A Model M, for example, has a membrane in it.