Practically speaking I rarely find GC pauses to be an issue, neither latency wise nor speed wise. Though of course that could be due to

1. I don't need low latency in research work,

2. I rarely work with massive complex data structures filling all my RAM where the GC has to scan the whole heap every time it runs, and

3. GC may have indirect performance effects that are not measures as part of GC runs, e.g. by fragmenting active memory more.

While I feel like I have my head wrapped around ownership well enough to write (dare I say idiomatic) Rust without too much difficulty, I do find myself often in a position where I wish I just had a GC.

I think this speaks to what your parent comment is saying: I think there are many situations where the performance improvement over having fine-grained control of my code's memory management is not worth the extra time I have to spend thinking about it. As it stands, I will sometimes give up and slap a bunch of clones or Rcs on my code so it compiles, then fix it up later. But the performance usually is good enough for my use even with all of these "inefficiencies," which makes me sometimes wish I could instead just have a GC.