Rwt, if you are not having fun racing crits then you should reconsider doing them. As far as danger is concerned road racing descents are much more risky than any crit I've done. The thing about crits is that course hazards are repeated hazards and unless you are in the break you are racing shoulder to shoulder for the duration. So riders that are not strong bike handlers raise the risk level. Road races are much more forgiving in this respect. As for attitudes, that's across the sport and varies with the aggressiveness of the event. You will also find that the higher up the ladder you go, the more mature and forgiving riders are. Nothing against you rwt but it's pretty easy to point out the Cat4's in my field. We've got a few real doozies out here.
The track is dangerous in its own right, especially in the sprint events that interest you. You want to talk about aggressive. When I race against trackies in crits I give them a little extra room and get by them ASAP. They will chop your wheel without a second thought.