I dont think there is "crappy" harris tweed... they tend to treat quality control seriously... there are a lot of variarions in thickness, surface texture (you might think hairy tweed is crappy), weave, pattern etc.
now crappy jackets made from harris tweed might be a different question... but even then, it'll last forever... I guess you'd really need to define crappy...?
That's right, so far as I know. The only "evil" surrounding HT was a cornering of the market, if you will, by some guy who tried buying up all the mills a decade ago or thereabouts. He was kind of the Henry Ford/Hunt Brothers of HT--you could have any color as long as it was one of the 4-6 he chose to weave. That's over now, I think. But, quality wise, I don't think it has ever been anything but top notch. HT may not be for everyone--a lot of folks think it looks like a bad rug--but if you like it, be sure you really like it, because it'll last pretty much forever.