I was tempted to hit crawl control on a 45 degree slope on Tuesday. I tried it with A-TRAC and the rear diff locked and started spinning and going to the right (which was a washout, and would have been a roll). Tried it without the lock, and made it further but not all the way.
I suppose in a pinch I could have done it if I had bothered to air down. I should have the vid of me trying this on Monday.
Me personally, I prefer going to 1st gear in the transmission in 4LO for most crawling, probably because I started out without that stuff.
ETA: