No, they never work.
At least they never work on a bolt that the original hex wouldn't work on. They work on bolts whose heads broke off due to fatigue; not over tightening or cross threading. The problems caused by broken EZ outs are worse than all the broken bolts they ever worked on.
They should only be used by the craftiest of craftsmen and only after one has resolved to replace the unit anyway.
Bosch Master, ASE Master, L1
33 years MB technician