When do you use 4lo?

I've used it many times. Pulled a stuck silverado out once before I had a winch. Mainly I use it to just go slow and ease my truck over stuff and down/up steep hills in a controlled way. That's just the way I drive, though. I go slow.
I also have a manual, so I feel like it's much more useful then because you can stay off the clutch until you're basically stopped.
I would never use 4low in anything other than 1st or maybe 2nd gear. If I want to go faster I just switch to 4hi. I think my manual says to stay below 15mph or somewhere around there. I'd have to check to get the exact number, but it's definitely slow.

 

I use it mostly in the winter when I dont feel like shoveling the driveway.