Well from what Randy's told me, the PTD is essentially what people have done in the past. I guess they would fill in the gaps between a couple of the pinion (or side?) gears with weld, so that it would lock up if they were differentiating, but then hit the weld.
Never heard that before, but I can kind of see where they are going with the PTD. The tech at Randy's said he wants to see it in operation before he buys into it, to me it sounds like the gov-lock almost. Not quite the same idea, but some slippage before it "activates" which would seem to me would load things up almost as bad as the gov-lock. When dealing with the small side/pinion gears and pinion shaft, I can't see it being incredibly strong. Tech also said they don't carry the no-slip, too many failures.
On a suggestion, I also checked out Pirate for results with the electrac, they are not good.
I wish I could test drive my rig with the various diff's to figure out what I like best. I have a feeling a lock-right etc. is in the future.