JB does work in some basswood guitars, but when it doesn't, it varies from one trick pony to useless. When it works well, it's brilliant at what it does. The upper mid spike is amazing for leads, not to mention great for cutting through live. Some guitars it even just sounds balanced in.
I have an SH-4 JB that used to be the bridge pickup in my ~'89 Ibanez RG570. It sounded bad there, cutting upper mids, but flubby low end, but no real highs or deep low end. Bloated yet nasal. With an A3 magnet & 0.75" hex screws under the wound strings, it's a fun neck pickup (fat for solos and riffs, but articulate enough for cleans). [I also have it with stud polepieces towards the neck, and the bass side screwed nearly all the way down and the polepiece screws adjusted to compensate, which makes it fat under the high strings but tighter and more bite on the low strings.]
I currently have a PATB-1b Original Parallel Axis trembucker as its bridge pickup, which has more deep bass yet isn't flubby, much brighter yet less piercing, with tons of harmonics and plenty of mid drive. Much more useful all around pickup that responds better to the tone & volume controls, not to mention pick dynamics.