markw, first off, I agree with you, but will add this...
the true trac can be locked by manipulating the e-brake and foot brakes... it does however add another thing for the driver to contend with. My experience with them has been that, to get the most out of them you need run the proper diff fluid, and gearing to the moon really lets you put the brake to them without stalling, or needing run the throttle. (I'm running 4.56's, a 4:1, and on 33's)
It definately takes some practice to be efficient let alone smooth. I'm guessing an automatic would allow a quicker learning curve, and the gearing would not be as critical.
At any rate, on the trail, ya, lockers are unbeatable... the true tracs can work as well, but, depend greatly rig setup and user intervention
... it took me several trail runs to get decent at them... and twice that long to get good at it.