So far, I have never had any problems with yukon. I live right down the road from randy's so I'm there all the time buying stuff from them.
I broke a detroit and Micah just had me bring the old one in and gave me a new one, no questions asked.
FiFo has also gone through a few sets of D30 gears (not my installs) but I know they were done right. (something about him getting cozy with the stupid pedal, oh, and the housing flex from his jeep seeing airtime didn't help things either) Randy's warrantied the first set, and I think he got genuine the second time.
As for the "crap" comment. I know a mechanical engineer that SWEARS by gears made with AMERICAN steel. Yukon uses steel made in india. That being said, I've broken lockers and axleshafts, but never had a R&P set go out on me. All the gears in my rig are yukon.