Flying cargo can be very different from one airline to another.
I flew MD11 for alitalia from 2001 till january 09. The last 5 years we only fly the freighter and it's been the best experience i had in my 20 years of flying. On the minus side, there was a very uncertain roster with very frequent delays, change of schedule and cancellations and many days out of home, but, if you don't mind this and also flying at night (remember: sun down-gear up / sun up gear down) it's the best job of all.