Mozilla has been participating in the design and development discussions of Houdini at the CSS Working Group since the beginning and continues to do so.
For Houdini as a whole ("CSS Houdini family features" that have published drafts per this issue), I think the most accurate current summary position is "worth prototyping".
As individual Houdini specifications technically mature (with web developer feedback & iteration) and assuming we see broader use-cases across the web, we can consider stating upgraded positions for each individual specification as appropriate, taking into account the importance of other web platform features.
If anyone has concerns about particular Houdini drafts that should block an explicit "worth prototyping" position, please speak up and we can use "under consideration" while we file issues on those drafts and iterate accordingly.
In addition, since https://github.com/surma ’s tracker was mentioned, this overall Houdini position should not be taken to apply to anything that is not yet at least a published working draft.
If an explicit position is desired for proposals in https://ishoudinireadyyet.com without a working draft, please file separate issues for those.