I run my backups overnight and get a status email each morning, and I didn't even realise there were performance issues until now. As you said, unless you run your backups multiple times per day, or have long-running backups, it may not have had a lot of impact.

FWIW, I live in Australia (so an 'off-peak' timezone), and schedule my cronjob on an odd minute offset, so it may not have been an issue for me anyway!