I would say gc:arc beta quality. Very usable for many programs, but needs more battle hardening. Please try it and send bug reports if you find them! That's how we improve!
> would you say "always use gc:arc" is a safe bet?
This is the first release to offer `--gc:arc` so there are still some rough edges, but I would follow @treeform's and @rayman22201's advice from sibling comments: give it a try, it might work for you without any problems, and if not - report it.
I would still try out --gc:arc on your programs. For mine it just runs without issue. But keep in mind if you do have issues you might have to create a bug report and wait for a fix. You would not reply on --gc:arc working. But it's fun to play around with. It's real now.