1. Those that make clearly audible and measurable differences. Speakers, headphones, and upgrading from total rock-bottom near-broken electronics.

2. Those that make measurable differences that probably aren't audible. Various super-low distortion figures on amps and DACs, or going from 320kbps MP3 to FLAC. Almust certainly not detectable by human ears, but instruments can see a real, measurable improvement.

3. Those that make unmeasurable differences that are not audible. These are obviously worthless and snake oil.

4. Those that make unmeasurable differences that are audible. These are either magic (none that I've seen so far), reveal limits to our previous understanding of audio measurement (these probably have existed at some point, but I'm skeptical that any current products qualify), or are actually #3 in disguise.

I think the worst you can say about Schiit is that their stuff falls into #2 -- measurably, but not audibly, an improvement over some other thing -- and since they relentlessly refuse to make official claims about the audible properties of their products, I think that puts them into solid respectability as an audio company. The worst you can accuse them of, really, is unnecessary metaphorical gold-plating.