It's been a while since I checked in on this thread. I did wind up getting the Shockstop seatpost and stem. The stem's effects are subtle, IMO. The seatpost makes a bigger difference, and I've got it set pretty firm. Both of them really smooth out textured pavement—there's something about the frequency and amplitude of the vibrations that they seem to be perfectly optimized for. The only time I really notice bobbing on the seatpost is when I'm mashing at low cadence on very smooth pavement.
Both of them are high-quality products. I don't see any slop in the pivots. The stem doesn't mess up the bike's handling. The seatpost is admittedly very heavy.
I am sure it is way different for lighter riders
Yeah. For comparison, I weigh 153 lb.