Absolutely! We've been using it as a special remote backend for our multi-TB git-annex repos, and it has been both painless and cheap. They have supported integrations for HashBackup and Rclone, and you can roll your own with their S3-ish (though not straight compatible) API. They have recently added native snapshots as well.

That said, as others have mentioned, b2's value differentiator is in cold storage. For us, it's largely insurance against failure of our other backup modalities. If you are pulling a lot of data back on a regular basis, the pricepoint is much more in line with the top tier providers.

Last I looked, the Free software python client worked fine. It was off to a bit of a rough start in the alpha release - but then quickly got some love.

Note that I for now tend to mirror data between servers/vps' I control/rent, so I haven't really used b2 in anger.