This is the initial beta-test release.
There might be bugs and we might still need API/ABI fixes but as of right now we do not know of any serious bugs (With the exception of #772).
This is not to be considered stable for use on critical data. That said, zlib-ng is running in some production environments, but those only utilize some of the codepaths and there might well be bugs in other codepaths (there are countless combinations with the zlib api).
Please test and report back your good/bad experiences here: #775
If you encounter a bug, please create a new issue with as much information about cpu, os, application as possible, and attach logs from compilation of zlib-ng (so we can see what kind of build was done) and any application logs related to the bug. If you have relevant test data that you can share publicly, that is also great.