I have owned the Salnotes Zero for a week and am here to share my impressions.
For $20, the packaging is solid. A plethora of multicolor eartips is included and, more importantly, the not-so-sturdy-looking cables are detachable. I find it very much welcome as cables are always the first thing to break from my personal experience.
The Salnotes Zero are more comfortable to wear than they look. I felt no pain or fatigue listening to them almost uninterrupted over a several hour trip. The isolation is also decent.
I am not familiar with budget IEM in general, the lowest priced which I confidently remember are the Shure SE115 which themselves cost 5 times as much, and between the two, I would pick the Zero without hesitation. That is to say, while I have never tried any of the Chi-fi killer budget options I have read about here and there for comparison, I believe they are well worth their price.
In terms of tuning the Zero has a good balance. While there is a decent amount of bass, they do not obstruct the higher frequency ranges. Rather, the mids are quite forward, resulting in a bright and wide soundstage. This, combined with the good instrument separation helps making the listener feel right in the middle of the music scene. Personally, I would have preferred a more V-shaped sound signature, which would have resulted in a more laid-back presentation. Still, I did not feel fatigued during any of my listening sessions, so if anything, tuning faults would be matter of taste. What was more unnatural though, is the dry, metallic, almost hollow timbre of music instruments in general. For instance, a violin vibrato sounds too flat, piano chords lack persistence, percussions and strings decay too fast, vocals are somewhat robotic and trebles are muffled. It is hard to tell in what kind of room an orchestra is playing. I guess you can only ask so much from such a cheap IEM set. Still, I am overall positively surprised by the quality of the Zero.
In my case they will stay in my workplace because they are perfectly suitable for voice calls. I would offer them to family or friends but not to a musician. They are easy to recommend to someone that prefers electronic over acoustic music.