Neuro issues are not bad in all specimens. Does the jag gene contain neuro issues? sure . . . but of the 2 jags I have neither show any symptoms at all. I have seen a couple adults that have intenese jagging, but it's going to vary by each snake you encounter. Buy from a reputable breeder and ask about jag syndrome in the parents of the snake and you should get an idea. There are two things you need to know though . . .
1) Stress induces the symptoms.
1a) Chemical stress may also induce - I.e. P.A.M.
2) Jag syndrome will generally stay hidden till a snake hits sexual maturity, around 2 years old. If you buy a hatchling and the owner says it has jagging symptoms. Stay away, it will be even worse later on in it's life.

Hope this helps.