[acid_rider]

RIDE Cycling Review said it did work

I think the theory is that the hole in the carbon fiber allows it to bend a little and the Zertz insert dampens the vibration. Who the hell knows if it works! There was a post about some guy popping his out and then noticing a stiffer ride but that's so subjective. Clearly it is a better seatpost than standard aluminum but I doubt you'd be able to differentiate between two different CF seatposts. Just ride.

IMO

There was a 2004 Roubaix Comp (Ultegra 9) road test in Australian RIDE Cycling Review (quarterly magazine) and they did say the Zertz did work well because the tester tried it on another bicycle and also reported improvement. The review for the whole 2004 Roubaix Comp was quite positive. The cyclingnews.com also reviewed Roubaix Pro 2004 (on pave in France, Aug 2004) and gave it 4.5 stars out of 5 and noticed it was very comfortable road bicycle. Whether this is all "in your head" I do not know but I test rode 2004 Roubaix Comp last week and it was a very comfortable package so I went ahead and ordered 2005 model (still to be delivered). I also test rode 2005 Bianchi 928 carbon and it was not as comfortable for me as 2004 Roubaix Comp was. Both were nice bikes but for me Roubaix Comp was much nicer (I am over 40 though, so allowances need to be made!)

It would be interesting to ride 2005 Tarmac Comp/Pro with Zertz and see if it is also more comfortable than other non-Zertz carbon road bikes but I leave this task for someone else to try 8^)