I like it because if you have the coordinates of a landmark, you can easily estimate the coordinates of other nearby locations entirely in your head, and the system encodes precision so you can indicate uncertainty.
https://en.wikipedia.org/wiki/Military_Grid_Reference_System
The top-level zones are its weakness. The further apart two coordinates are from each other, the more difficult it is to reason about their relationship. MGRS works fantastic for reasoning about coordinates on the same grid square, but gets harder as you move up to comparing between grid squares and harder still as you compare between zones.
A grid square is 100km x 100km, so it's pretty big, and coordinates in the square are easy to manipulate. If you know your office is at 4QFJ 21631 04440 and the Starbucks is about 500 meters down the road to the north, then you know Starbucks' coordinates are roughly 4QFJ 21631 04940. To indicate your uncertainty, you'd say 4QFJ 216 049, or possibly just 216 049 if the grid square was already known from context.
The system is typically extended to allow that reasoning to work even at the edges of a grid square, by allowing eastings and northings that extend past the grid square edge. This means there's more than one possible way to describe a location, though only one canonical way. Unless you're already familiar with the area, you may need a map to compare coordinates on different squares.
Some of the grid zones are also a little oddly shaped. It's mostly not a big deal because they're huge, and it really only affects which coordinate representation is the canonical one at the boundaries, but it would be nice if the top-level 6° by 8° grid zones were more regular.
Who knows how far away epic.region.music and epic.global.music are from just the names? While 18SUJ2163104440 and 12SVC0452723150 are 6 grid zones apart east to west.
It's actually quite pleasant to use and allows you to just truncate to the level of precision you want. S/He just posted the 1m resolution string when 18-SU-J-216-044 would get you to 100m.
All this said, I think the real issue is that we refuse to PICK a standard and so every device with a GPS and ever map has one or two of
-MGRS
-UTM (almost identical to MGRS)
-LL DD MM' SS.ss"
-LL DD.dddd...
-LL DD MM.mmmm...'
etc.
If you make a device that can output or accept a location string, make sure it can handle all LL cases and UTM/MGRS.