I guess i was trying to ask: how often do you have to divert because of bad weather, and when you do what (if any) consequences would you face?
Great question. Just as my Airnet counterpart said, safety is relative. My good friend Jtrain has been flying out west with Ameriflight. Well, let's just say that most West Coasters will freak out at the first flash of lightening or boom of thunder.
However, if you fly freight down in the Southeastern U.S. for a while, you learn just how close you can get to a storm, just how to read the radar, and how to tell just how much you can tango with a nasty line.
EatSleepFly flew quite a bit of freight up north. So, while I've dealt with a great deal of ice in Tennessee, he's probably got a much better understanding of icing, how to get out of it, and how much is too much.
In my time with FLX since April of last year, I've cancelled one day of flying. Our dispatchers (i.e. flight followers - they have
NO legal authority) gave me crap, and transferred me to the D.O., hoping that he'd force my hand. His answer? "If you don't think it's safe to fly, don't fly". That was the end of it.
Also, one night last fall/winter (I don't know the seasons very well . . . I'm from California!

, I tried to work my way through a line between Atlanta and Nashville, and ended up turning around and landing back in Atlanta.
Like Mikecweb said, if it's safe and legal, you're expected to do it. If you're in an airplane equipped for flight into known icing and there's icing conditions, you're expected to man up and go. Now, if the anti/de-icing equipment on your plane can't keep up with the rate of accumulation, then it's not legal. Otherwise, you have no excuse.
Thunderstorms in the area? That's not a reason not to go. A line of thunderstorms? That's not a reason not to go. A solid line of severe storms with tops at FL450, no holes, tornadoes, hail, etc? Well, maybe you'd better wait it out.
All of that being said, the whine factor tends to be pretty low among the freight guys and girls. We learn what the limits of the pilot and the machine are, and we walk it, staying just on the safe and legal side.
Either that, or you die.