zstd and xz trade blows in their compression ratio. Recompressing all packages to zstd with their options yields a total ~0.8% increase in package size on all of their packages combined, but the decompression time for all packages saw a ~1300% speedup.
We already have hundreds of zstd-compressed packages in our repositories, and as packages get updated more will keep rolling in. No user-facing issues have been found as of yet, so things appear to be working.
As an end-user no manual intervention is required, assuming that you have read and followed the news post from late last year.