@AMoody: I used to measure the weight of Model M keys. You'll find a range. "Identical" boards can vary by 10g; different keys on the same board can vary by a few g. I don't know why. Unicomp springs feel crisp compared to old worn-out springs. Old IBM springs that are less worn also feel crisp.
Whatever makes them feel crisp, it's not the peak force, as that's the same, about 75g typically. Maybe they buckle higher up? I don't have the equipment to produce a force-curve graph which would tell us what's going on. Wouldn't that be fun?
I'm recovering from RSI. The formula has been: Kinesis contoured keyboards, 45g cherry browns, touch typing, Colemak layout. I alternate between a Logitech m570 trackball and a Contour Rollermouse. I alternate between sitting and standing, and wear Ace brand Deluxe Wrist Stabilizers to sleep at night. If you have pain, stop worrying about the weight of your Model M, buy all that stuff and spend a month adjusting to Colemak. It works! :biggrin: