In practice I've had overwhelming feedback praising our use of spinners in the Heroku CLI and not a single complaint I can think of. In fact, I've had more praise for adding spinners and color than any other change we've put in over 4+ years of development.
That said, you need to be careful. Don't use a spinner if it's not a tty or TERM=dumb. Do use it in some CI environments that support it (Travis, CircleCI) That handles all the issues we've seen and everyone seems to be happy.
That said, you need to be careful. Don't use a spinner if it's not a tty or TERM=dumb. Do use it in some CI environments that support it (Travis, CircleCI) That handles all the issues we've seen and everyone seems to be happy.