DH is 175-180 lb, a bit of a masher, does a little racing and gets about 6k out of DA chains. He actually doesn't replace the cassette everytime either, says it still shifts just fine on the original (although next time it is getting a new one). That is the only experience in our house with them but enough for me to say I guess that aren't as fragile as said. He does keep it regularly lubed and since we are in Texas it is mostly dry weather riding. I would think that does factor into wear.

I run an Ultegra chain but I really don't know my head from my butt on this stuff so whether it is better I wouldn't know.