We have had a pretty good but not great experience with JFS over the past 18+ months.
Our strategy must support the major Linux distros (most of our clients run CentOS, RHEL, Ubuntu or Debian), and since XFS and JFS are both equal “cousins” on the Debian/Ubuntu side of things it just makes sense to prefer XFS. ext4 is still a bit immature for our taste.
Furthermore, various performance benchmarks including this one generally give both high rankings
We will implement this strategy through attrition rather than by any kind of forced retrofit.