Couple of general comments and some links to useful resources.
I think there are 35 "shall-issue" states.
In general, concealed means concealed, and one could get in trouble if exposed.
In general national violent crime rates have been going down since about 1994. The anti-CCW people always said carrying weapons would turn our grocery stores into war zones. Obviously never happened. Crime from permit holders is almost non-existent.
In my state, Arizona, violent crime rates peaked around 1994 when the shall-issue CCW laws were enacted. Violent crime has been trending down ever since. Some other non-violent crimes however have not really declined - like car theft.
Good resources are:
http://www.packing.org/
State-by-state CCW laws. Not much on crime stats though.
http://www.ojp.usdoj.gov/bjs/welcome.html
If you want to do your own research on crime statistics, go here. The Bureau of Justice Statistics. You can download spreadsheets by state or for the whole country.
http://www.rkba.org/ccw/shall-issue.html
Good article on analysis of statistics.
-- Dan