Wow that is expensive for a lunchbox locker. If you had a 31 spline 8.8 you could buy an aussie in the 200's. Shop around. It is not a glorified limited slip, it is a LOCKER.
When you accelerate moderately, the torque will make the locker full on lock and not allow the left and right to turn at different speeds. As you are light on the throttle or coasting, it is like an open diff. Read up on the aussie locker on here, it is the same thing and there is a lot of information about it.
It is great for extra traction on road and off, but technically it is not safer in the rain, snow etc. Reason for this is because it will cause the truck to over-steer in slippery conditions. This isn't always bad, you just need to be prepared for it and know how to deal with it. A lot of people run these lockers on a daily driver (I use to as well) just fine.
Also, these types of lockers work much more smoothly with an automatic. With a manual, picture yourself accelerating and shifting gears through a turn, such as a long intersection. As you start accelerating, the locker is locker, and the tires scrub a little as the truck wants to go straight. As you let off to shift, the locker unlocks and it steers much faster and unloads the odd load on the suspension and drivetrain. As you begin accelerating again it locks and the truck will lean more as it is trying to go straight. This will not only make it uncomfortable for -some- people, but it will put a lot of strain on the weak 7.5" axle.
With an automatic it will just stay locked and scrub the tires a little.
$400 is a lot of money to put into a weak axle that is likely to break with a locker. You can get 8.8 axles (or an explorer 31 spline 8.8) at a junkyard for cheap, and buy a new aussie locker for cheaper for it.
Anyway, I loved having front/rear aussie lockers in my sport trac daily driver automatic, but you need to research how they work. Ask Shane how much he likes his aussie locker with his manual transmission.
2006 F150 FX4 Super Crew - Bilstien 5100s leveled 2", 35" KM2s, 4.56 gears, Detroit locker, Eaton E-Locker, Traction Bars, AEM intake, Xcal 2
2010 VW Golf TDI 6MT