You will probably get some much better answers from the more seasoned freight pilots here, but heres what I have to offer.
I fly the Baron, Caravan and Chieftain at Airnet. I've been in icing conditions in all 3 of them as well. Nothing to serious in the caravan though so hopefully Mike or Stone Cold will chip in for that. I can tell you though that the Chieftain and Baron are great in icing. Not so much the equipment even, just the fact that each of them can really haul a load of it(Chieftain/baron that is). The boots on most of the ones I have flown are so so. Sometimes most of the ice comes off and other times just bits will blow off and your left with leaving it on there or trying a different altitude to melt some off (Usually doesnt work for me).
Overall I would say the ice equipment on the planes is enough to give you options in getting out of the ice, or staying in it for a short period of time depending on the severity.
Oh and one more thing, we arent even legally allowed to launch into forecast or known severe icing, so your offered a bit of protection there. The training goes really in depth in dealing with it, so you will be ready to deal with it. EVERYONES main concern in flying freight is weather so you are not alone, its just something new for most people.
As for launching into weather, I have never cancelled a flight yet. Again the more seasoned dogs will have better answers for you. I have talked to guys who have landed in 40 + knot winds in blowing snow, yadda yadda, but hey no one ever says you HAVE to go.
I remember hearing a story about sometime last spring all of our guys in the south refused to fly because there were tornadoes and hail everywhere, and no one got fired then. Thats the best part about the job is YOU are PIC and whatever decision you make is the one that goes.
Hopefully that helps, I myself am looking forward to some of the other answers because its still a constant learning game for me as well.