It works fairly well, although it has not the swinging feature, and if you want to turn upside down the goose neck, you have to turn the counterweight lever horizontally at the same time with the other hand. It started life with two twin weights, but in the end I found it better to eliminate one of them, leaving a single one at the most extended position. It reduces notably the drag of the needle, and one can play more records in one single winding. This is the first real advantage I've found.
The bamboo lasts longer, perhaps, although it depends strongly on the point. I usually make my own bamboo needles, and the good ones work as well without the counterweight. With the good ones I can play several sides without repointing. Of course the record modulation is a determinant factor, as also is the kind of surface. I'm not yet able to define the effect of the counterweight when using bamboo, although overall it seems to ease the needle travel across difficult records. I've also noticed the important role of the soundbox weight in polishing the point against the grooves, and the counterweight acts against that. As a preliminary conclusion on the advantages of the counterweight when using bamboo I can only point out the lesser record drag and the easier needle travel on difficult records.
The steel needles also seem to collect less record dust at the end, but only in difficult records. I always use soft steel needles (purchased by the thousands from Mike Child and Barry Williamson many years ago). I mean that on easy records the effect of counterweight is not noticeable. With the 5B soundbox I use, on easy records there is no black dust at the end of a side. The record drag is lesser with steel than bamboo, of course, but this is only noticeable with worn or difficult records. Again, the most immediate effect of the counterweight is simply this one. The motor has an easier life and a winding plays more sides with the counterweight.
Anyway, still I'm experimenting and learning about it.
I show it herein as a curiosity, if you want... but it works as well as any commercial device. Still I must improve it to be able to turn up the soundbox with ease.
Some photos here. They are more or less self-explaining, but any questions or detail requests are welcome.