SoundSmith cartridges how good?

It depends how many decent cartridges you can audition, you can always find a better cartridge. 

And there's the problem. Very difficult these days to hear many different cartridges let alone on same arm into same phono stage. 
Appreciate the above responses so far.

I like Peter and his business model and have owned the MIMC Star (original version). It is a good cartridge but I feel that the Soundsmith line is now overpriced and there are other cartridges that represent a better value for money. For example, the ART 9 which I ran before the MIMC Star was half the money and at least as good (better actually in most ways). However, IF you plan to buy, hold, and retip then the value of the SS carts is hard to beat.

I love my Zephyr. Very neutral and natural to my ears, definitely not in the least ‘bright, as mentioned, tracks very well, (I can play a fairly warped LP and my SoundSmith Zephyr is practically unphased compared to others), and refined and detailed. Also, compared to my others, the Zephyr never seems to get ‘overloaded’ or ‘overwhelmed’ with the information in the grooves even at higher volume. Just incredibly solid and not the least bit ‘wobbly’ in its presentation. In addition, I find the Zephyr incredibly quiet, and easy to set-up. It doesn’t seem overly finicky about ‘perfect’ adjustments, and gives great sound with little effort other than the basics.

I bought a Goldring 1042 not so long ago as a back-up. Has a very similar sound signature to the Zephyr, and am incredibly pleased with it (at a third of the cost of the Zephy). I was actually quite amazed after first listening to it, and it did cross my mind, ‘why not sell the Zephyr and use the Goldring instead’? I became a huge fan almost immediately, and actually left it on my arm for a week or so. Then, I put the Zephyr back on, and quickly realized just how much more quiet and sophisticated it was in comparison, and provided overall performance the 1042 cannot really equal. That said, a great back-up cart, and can not recommend it enough at its price-point. I’ll be able to live with it quite easily when the Zephyr needs retipped.

Peronally, I don’t think you can go wrong with a SoundSmith, but as everything, it’s all subjective.

How good are Soundsmith cartridges? Good enough to be next in line, and end of the line, for me. When ready to replace/upgrade my Koetsu Black Goldline it will be to a SG1. Which also makes it the upgrade for the Herron.

Why? Because, if you do the research you will find what tablejockey said, SG1 is up there with all the very best and VERY costly SOTA carts, but at a fraction of the price. Considering you are getting both a surpassingly fine cart and phono stage in one, for less than the cart alone, or the phono stage alone, would cost with the others, a very small fraction indeed.

But if not a SG1 then one of his more normal MI carts. But seriously, it will be the SG1. So yeah, Soundsmith is pretty good.