i had one on my savage, this is what i experienced

pros:
a bit more traction on off road surfaces, works good in sand
power doesnt go to the wheel with less traction
you ALWAYS have 3 wheels with power instead of 2(unless your running rear wheel drive)

cons:
More likely to break a dog bone/cvd
not good for onroad
not good for jumps, cause if you land with just about any amount of throttle you'll snap a dogbone/cvd

I like them, but i would only run one in sand. Im gonna run 100K in my savage diffs, will give it more traction but the diff will still be able to offload if its needs to.