With all respect to Rod, who of course is free to feel "bowled over" as he puts it, I would like to repeat that I was pleased by the effect of the bullets which they had on my system, I bought a pair after all, but on my stators the effect was not that huge. I have been using Bybees of all shapes and sizes right from the beginning when they first came out. I have always noticed a positive effect, no matter where I put, or soldered them into.It generally made the music a tad more "real" to my ears. Swapping ICs or rolling tubes had however generally a greater effect in the sense of being "bowled over". The reason for this seems to me, that by doing so the entire musical presentation of your system can be changed. Not so with the Bybees, their effect is such, that the voicing of your system will be the same, but there will just be a tiny bit "more" to heard of what your system -within its limits - has to offer, is capable of. As I said, the musical presentation seems to be a bit more real to these here old ears.
By the way, the best way to test the effect of these devices I found, is not only to compare the sound with or without them in the chain, but to compare just one channel with and the other channel without them on a mono recording in your stereo. You will notice the effect quite easily, because the channel with the Bybees will have more presence somehow. You can even increase this effect slightly, by using more of these things until there is no more difference discerned. Again, the overall effect is slight, but certainly there. If it is worth the cost lies in the ears of the listener.
Cheers,
