In 2wd, you will not feel it at all. You WILL hear it though. Clicks around corners.
I would think about a Lockright or a Spartan locker before the Aussie though. They might be a touch more $$$, but the availability of parts/service is far greater all over the country. I tow my Jeep to places, and if I were ever to break something, I would want to be able to get parts locally. Aussie availability is very limited. Most places stock Lockright and Yukon stuff.