phototristan, I felt exactly the same way—that the new Hybrid felt much lighter than my Pro 2, but what Sup said is correct. I have two Pro 2, both over three years old, and they're both much stiffer than the Hybrid. I think I've just gradually grown accustomed to the aging domes, and have forgotten what new domes feel like. After a week of breaking in the new Hybrid, I actually prefer the lighter action now. I can confirm that all the new Hybrids are similarly light. I bought two Hybrids and two Hybrid Type-S (don't ask), and all four are much lighter than both Pro 2.
Regarding the sound difference you mention, on mine the main difference is that the upstroke clack is much quieter, but I think over time, after the rails are broken in, the familiar clack and and rattle should appear. Place your old Pro 2 and the new Hybrid side by side, and slide your fingers across the top of the keycaps. Notice how much looser and rattly the Pro 2 caps are? (Incidentally, when I do the same with my Hybrid with Hybrid Type-S, both brand new, the Type-S caps are much more stable with much less rattle.)
BTW, Fujitsu Computer Products of America (fujitsuscannerstore.com) doesn't take returns. I found out the hard way. I only need one set (one Hybrid and one Hybrid Type-S), so if you're serious about trying the Type-S, let me know. I need to sell both of the old Pro 2 and one each of the new Hybrid and Hybrid Type-S.