I have been going to mine once a month since mid 04 and have had no neck problems from adjustments { he is very gentle and precise with any adjustment and very good - IMO}. No grab and crack with him!
{avoid those types}

I think it really depends on the chiropractor and his technique/skill level as well as his care, caution and concern.

And of course they shouldn't adjust before seeing recent xrays - to be on the safe side that no problems are showing there.

Maybe ask that he adjust other places if you are concerned - until you feel confidant and can relax.
- mine won't do the adjustment if he feels like I am tensed up,he waits a few seconds or says something to me - usually I'm thinking about other things and not relaxing.