I’ll also throw my hat into the ring for this. Prior to properties being released I managed note metadata with inline dataview fields, largely because this gave me more control over the aesthetics and organization of metadata in my notes.
I like the look and features of the new properties system, and started updating my PKM worflow to use properties instead of inline dataview fields, but I ran into an issue of poor aesthetics and usability / readability in the properties UI when the number of properties grows large (see Properties UI: add option for inserting visual elements to help visually group related properties). Thus the ability to nest properties seems really important for both aesthetics and functionality, especially when the number of properties in a note is large.
This has caused me to hold off on further integration of properties in my PKM until the nested property issue is handled, as I find it’s not feasible to use properties as it’s currently configured for notes with many properties.