I run a mini spool in my rear Dana 44.
Advantages: Cheap, awesome traction, just like a locker, predictable on the street but on the long wheel base XJ with an auto that isnt much of problem.
Disadvantages: tire wear I have used up half of my Timberline MT's in 9 months (admittedly a very soft compound). I rotate every 1000 miles and limit it to 50 miles or less per week when possible except for wheeling trips. Its tough to parralel park (needs a lot of throttle when cranked over and the jumps back when it unloads). Hard on the springs. I run soft long travel soft springs and they wrap a lot so I inspect them monthly for cracks (none so far). The U bolts need tightened every few weeks due to all the wrap (yes I use locktite).
Bottom line: In two years what you save on a mini spool (let alone a full spool with set up costs) you will spend on tires, faster if you daily drive. I will be switching to a Detroit, ECTED or other part time or auto locker this winter (ECTED because I will be in Va with snow and ice).
John
