Eaton Lock-Right in a 2wd 1-ton Ford van. I've been towing with it for 4 years now (owned it for 6 or 7, bought sleds 4 seasons ago). It does surprisingly well in snow - here in CO, the airport shuttle companies that service the ski areas all used Ford 1ton vans - figured they must be good. They are. I use studded tires & carry chains; typically only have to chain up on FS roads/parking lots. Only had to use chains on public roads a couple of times, and that was in Denver after 3 or 4 2' storms in a row (Christmasish 2005?).
That said, when I _do_ need to chain up, it is a pain in the butt, and 95% of the time, I found myself thinking a locked rear would have been enough. A couple of times last year the locker would not have been enough by itself - driving up to the Buff Pass lot after ~11" in town, 18" at the lot, first one up the road - needed chains for that no matter what.
I'm curious about snow behavior, too - the internet is largely of the opinion that lockers are "scary" in snow. Dunno about that. I can control when it locks, and as long as it is predictable, I think it'll be fine. I drove it on a pretty slick snowpacked road last weekend, I'd have gotten there with the open diff, but with the locker, it was _effortless_. So far, dry roads are 100% fine, and low speed ice/snow traction is greatly improved - the big question is snowpacked, icy, 40-50mph I-70. With the open diff, the van was absolutely fine in those conditions - I can only remember getting wheelspin once or twice in the time I've had the van (used it for skiing before sleds), typically at the Eisenhower tunnel, typically in traffic going 5mph. Highways are not normally an issue.
Dunno. If it spins both wheels, it steps sideways. It already did that, it just does it more with the locker (intentionally lit them up last weekend on the snowpacked road, it stepped out, no surprise, lifted, it tucked back in. No big deal). It is just a matter of predictability, and basically, as long as there's torque on the crosspin, the diff is locked. It can't unlock if there's torque on the crosspin. No torque, open diff. So, basically, be gentle with the throttle on slippery surfaces, and if it DOES lose traction, the rear end will slide downhill.
We shall see. Hoping the roads get snowpacked tonight, but the forecast is not looking good for that. Worst case, I put the spider gears back in & save pennies for an ARB. IMHO, a _good_ limited slip is going to behave exactly the same way - I just don't buy that the locker is going to magically lock and unlock as you're driving down the road.