I guess depends on where you're comparing it to. We moved up from sydney; thus in comparison Cairns is a lot better. You do get your odd crime here and there but not much compared to other places like sydney. The other key aspect i think is picking the right suburb. ;)
Inner city including M suburbs, Bungalow and Parramatta Park are hot spots. White Rock and Mount Sheridan are also no good. Check QLD police site to see the reports. The figures don't lie and the patterns are obvious.
As at April 2012 The police here have had a drive to catch and prosecute those few (families) people ythat are always doing burglaries and petty crimes. It's worked a treat. The Cairns City Circle, as defined by out to Edge hill and about Cairns North and somewhat past Stocklands, is quiet, safe and very pleasant o live in . The large apartment blocks in Manunda and Manoora area are providing terrific value ($140-20k) and are good safe areas to be in. Probably once a bit iffy, but great now.