Well said, Richard...that pretty much sums it up. I heard the same thing from Dustin Webster when they were out here at Rausch Creek for that comp over the summer...he was watching us fool around on the comp course and suggested I try doing some stuff in front-wheel only (rear is a Detroit in mine). I was amazed at how much more agile and sharp the rig felt without having the rear pushing all the time.
On a stock or mild XJ that sees mixed street and trail use, here's how I look at it. Putting it in the front will make the greatest difference offroad, but also makes it more likely to break D30 parts and can be a handful in the snow in 4WD. Putting it in the rear won't help as much, but it's a more traditional street driving experience and if you have a decent (not D35) rear axle it's pretty safe as far as breakage goes.
I did a rear one first when I was running a D30/D44 on 33's. It definitely helped, but the difference when I put a front locker in was huge.
