Just to add my 2 cents, I now have an Aussie Locker installed in the front axle of my '98 TJ and I left the stock rear diff open. To me, I have the best setup without going to more expensive selectables.
The front axle has the most weight (engine) so it will provide the most grip. This makes the most out of the fact that the wheels on that axle can be locked together.
The front axle is part-time. If I don't want the wheels locked, I simply move the lever on the transfer case. Call it a poor man's selectable lunchbox.
As for the rear axle, if required, I can utilize the handbrake to move torque to the wheel with the best grip. Call it a poor man's locker.
The advantage is the rear is left open, so no squirrly handling to worry about.
BTW, I have subjected my front aussie equipped TJ to every imaginable surface condition ( other than dry pavement where it doesn't belong anyway) including deep snow, packed snow, sheer ice, ice ruts, off camber roads with ice, icy curves and icy uphill grades and I can honestly say this thing is fantastic. It WORKS perfectly, no darting or jumping, in fact, I wouldn't know it was there except for the tremendous traction I now have and just a bit more steering effort. It is great...up front!