RAM 3500 Off-Road Capability: Can it Handle the Tough Stuff?

I've been eyeing a RAM 3500 and I'm curious about its off-road capabilities. Has anyone pushed one to its limits on rocky trails or muddy terrain? What kind of mods or equipment are needed to get it through rough stuff? Is the 4x4 system reliable, or does it falter when faced with steep inclines or deep ruts?