For me they were one trick ponies. They did one sound, it wasn't bad, but I had learned how to make passives work for me. EMG's didn't jive with that. I also don't like batteries, and the idea of a pre in there is another thing to go wrong. After going through the 500 series of mic pres, it is easy to see that they can make a lot of difference. Their pickups work for some people, but not for me. They were not sterile, they just did one sound, very little dynamic range. I have also played passives with crappy dynamic range, but they always had more. That suits my playing better. So no battery, more dynamic range, and no pre.
After I got in touch with Ken, and got to play with one of his sets of pickups, I had found my brand. That was a revelation, they are passives, but there is a whole different world of depth to them. Makes it fun to mess with picking, volume, and details that seem to get covered up more by other pickups. Not to say that those things are not there with other brands, there is just so much area to play in with Kens pickups. And on top of that, they are not absurdly priced, they are very reasonable.
Patrick