(Serious) problems with the stock bridge:
- Too heavy
- Forced me to shim for a decent action
- Hard to fit strings through (especially B)
- Strings don't align over pickups
- G string falls off the neck
(Trivial) problems with stock knobs:
- Too many similar knobs
- Risk of turning the wrong knob on stage
I recommend those mods (especially the bridge) to all Ultra Jazz owners. They really made a difference for me. Now I enjoy the bass much more.