Great engine. My neighbor has one to pull his camper and he loves it. I think Ford's got a real winner with the 6.2 and so far reliability has been great. Most people are recommending to get the 4.30 axle but they're hard to find and with the weights you're planning to move, the 3.73 axle may be just fine. For mileage I included a link from Fuelly.com of actual users getting well over 12 mpg's in mixed conditions:
http://www.fuelly.com/car/ford/f-250_super_duty?engineconfig_id=299&bodytype_id=&submodel_id=
Here's another link from actual owners discussing 6.2 topics:
http://www.thedieselstop.com/forums/f154/
Finally, you can always check Ford-Trucks.com for more 6.2 talk:
http://www.ford-trucks.com/forums/forum206/
Good luck and enjoy the new truck!