I've been using them as backup storage for a while (their B2 offering to be exact) and it's been working fine for me.
Really can't complain about the price, most other providers are more expensive or have specific conditions attached.
I use them for an online copy of my backup. They're very cheap and I've got nothing bad to say about them. I use rclone to sync a local borgbackup repo to it, which gives me a couple copies for redundancy.