Well, threw the bike on the stand to lube the chain tonight and discovered two things.
1) The B-tension screw was all the way in, pushing the derailleur pretty far from the chain.
2) The chain was too long - going slack on the 10, so I pulled out two link pairs, probably could have done three.
After these two things were fixed, a little adjustment and it's running nice and quiet now. Pretty awesome that the bike shop was unable to find these things. ಠ_ಠ Oh yeah, maybe that's why I do my own work. That, and when the bike was delivered, the low limit screw was set poorly and allowed the chain to jump the big sprocket into the spokes. Thankfully my quick reaction and the the straight pull spoke design kept the chain from getting wedged in or chewing up the spokes. (there you go, the first valid reason for straight-pull spokes!)
Also kinda annoyed that I missed it the first time around, should have noticed both of those things. We'll see if it's fixed next time I take the bike out, but it's quiet on the stand, and that's a first.
Had wondered the same thing about this new riveted cassette, think I'll probably start watching prices on the XX1 cassette. Still, having found what I have, I don't think it's the cassette's fault.
Crank shouldn't be an issue because crank, BB, chainring - all of them are bone stock as delivered from Specialized. Chain is as delivered as well - KMC X11L.
Craig, I'd check for the same things on yours - Shimano chains on Shimano cassettes should be _silent_. Shimano chains are some of the best I've worked with, but the pin design on those is a pain in the ass, and I find KMC chains work great, so usually run those.
Thanks all for the help!