> For the second type of system, I can't remember the last time where I wrote one where I had in-process parallelism/concurrency with shared resources (even in langs where there's no GIL). It would just get too confusing and hard to reason about. Any optimizations were mostly based on intelligent batching. For parallelism, you'd just have multiple _completely_ independent processes, probably across multiple machines.
For myself, the prospect of no-gil is interesting, in that something like my Captain's Log application [0] can be free from it; for example, I currently use a QThread to implement a JournalParser, which is basically the program's "engine" - the parser constantly reads in game events from a player journal file generated by the game Elite: Dangerous (and Odyssey), and depending on the particular event, fires off a related custom QSignal, which is then processed by whichever slot (receiving function) is listening for a given Signal.
There are other places in that application where no GIL might be quite handy.
In other words, I can see where having no GIL can be useful for GUI applications like mine.