I had a 4 roundtrip email thread with their support over a speech API bug. Eventually sent them a narrated step-by-step screencast, and the guy is finally like "oh, it's not supposed to work that way." (Yes, that's what I said in e-mail 1!)
For copying photos off an SD card you're unlikely to notice any difference on any machine made in the past 10 years, except maybe the fans coming on, but try it on a Raspberry Pi class machine, or doing any kind of random IO and oh boy..
The Spectre/Meltdown situation must have made FUSE much, much worse than it was already. I wonder if anyone did any benchmarks for that
The trouble is how they compose with the expectations of code you don't write. It's just not normal in C to expect execution of your function to abort halfway through, and so memory leaks and broken state are almost guaranteed when they're mixed with the wrong third party library.
It might work great when you wrote it, but it might not even survive the next change to the codebase, and 10 years out, who is to know what programmers will come along and plug new stuff in without noticing the stack magic, etc
edit: another aspect of the same issue is that it can be difficult or impossible to write generic longjmp-safe code for many kinds of tasks. In C++ you have stack unwinding to e.g. delete large temporary heap allocations during a complex operation, but no such facility exists in C.
These are used /everywhere/ in PostgreSQL, exactly for exception handling. The result isn't bad at all, but indeed, too powerful a tool for 99% of developers