It's certainly not soft or spongy on the bottom, where the action is. It is spongy on the top, when the finger first contacts the key. The bottom of the stroke feels exactly the same as the rest of the keys, but a bit more evenly spread out across the fingertip.
Tap your fingers a few tens of times on the plastic casing of your keyboard, then tap a few tens of times on a leather wallet or jacket. Feel the difference? That's what I'm typing on!