According to my previous experience the choice of tailpiece does not make too much of a difference to the sound. I usually stick to the Bois d'Harmonie because of the superior fine tuners and thought that pernambucco and their tailcord had a positive effect on the response and sound quality. I never thought that the difference with the much cheaper Akustikus was very big though. My new cello came with a Wittner composite tailpiece, and although it is quite light I always found the short distance between the strings to dampen the resonance. So I mounted a Thomastic metal one I had lying around. I think it came with my old L&C cello because Luis wanted a tailpiece with a big distance between the strings. He felt the strings should go in a straight line (parallel) from the bridge to the tailpiece to reduce the damping effect of the afterlength. The Thomastic worked better than the Wittner, but I had the feeling the weight (98gr?) reduced the quality of the sound. So it was time for a new tailpiece.
It has probably been 6 months since I first discovered this tailpiece on the internet, but it proved very difficult to get hold of one since it was always out of stock and with a long leadtime. Finally I got lucky though, but I had to pay €119 in stead of the cheapest offer of €77.
It is only 58gr, so much less than the 77gr of Akustikus or the 70gr of Bois d'Harmonie. The finetuners look great, but the action is not as efficient as the BdH ones. Still OK though. The finetuners are a bit too close to the string holders, which can make the tuning a bit awkward for people with thick fingers (i.e. all cellists), but this is again not a big problem. The finetuners are even further apart from each other than on the Thomastic tailpiece, so with that respect it is probably the most extreme one on the marked. Overall the Herdim tailpiece looks spectacular and exclusive and is of much better quality than I expected for the price.
I never before heard such a big change to the sound from a setup change as with the Herdim! To put it short: It added some of the best features of the L&C to my cello. The response improved a lot; The cello simply became easier to play. The sound opened up, and the cello resonates more freely and carries even better in a big hall. The volume is bigger and the sound is richer. These improvements are the most apparent in the bass. The top register does not seem louder than before, but the sound it definitely smoother and with more texture. Highly recommended so far, but every cello will probably react differently too such a light and resonant tailpiece, and it will never be to everyone's taste.
Edit: I tried to upload OK versions of my own pictures ca. 1 trillion times but failed miserably so far, so here is a link: