My 93 4x4 cc IDI has automatic hubs. I plow with this truck and LOVE the auto hubs compared to my previous truck - an 85 F-250 5.8 with manual lockers. I had to replace the manual hubs on the old '85 at 100,000 mi. (probably 30,000 miles in reverse!) Anyway, the manual ones can fail, too.
It's nice not to have to get out of the truck. It doesn't sound like such a big deal, but having had both types, it REALLY makes working easier.
I think my auto hubs are failing, though... Once in a while I hear a pretty nasty clikcety clankety CLUNK CLUNK CLUNK up there and have to put it in 4wd, pull up, pull back, put it back in 2wd and it's been ok. This has happened 5 or 6 times in 2 years. Also, sometimes it feels like it has to "spool up" a bit before the hubs engage - then it kind of bangs up there. I don't like that sound, but I'm just planning on replacing the hubs when I do the rest of the front end next year.
Does any company make really nice HD auto locking hubs for our trucks??