Currently, not that much.
So far, they've only launched Hidden Service support for their DNS over HTTPS (DoH) service.
What it means is that rather than transiting the open internet (whether directly or passing through Tor first), your lookups can go to their resolver without leaving the Tor network. That's a good thing (reduces usage of the limited exit node bandwidth, provides strong authentication that you're talking to an authorised server etc).
What they haven't launched (I suspect the word yet applies here) is support for hosting hidden services via Cloudflare. Though why anyone would want to....