Concurrency is *hard*. There's no getting around it, there's no
sugar-coating it. There are concepts that simply have to be learned,
and the failures can be extremely hard to track down. Instantiating an
object on the wrong thread can crash GTK, but maybe not immediately.
Failing to sleep in one thread results in other threads stalling. I
don't think any of this is changed by different modes (with the
exception of process-based parallelism, which fixes a lot of
concurrency at the cost of explicit IPC), and the more work
programmers want their code to do, the more likely that they'll run
into this.