I've used JFS for years, at least 4 years. Haven't had an issue yet. I don't run mythtv, but do, do a bit of dvd authoring. So that includes lots of writing then removing of files. Speed and overhead are better than ext(2/3) and reiserfs.
I personally have very little xfs experience. Last time I used XFS was shortly after Suse included it way back when. Version 1.x something, completely unstable. Many, many improvements have been made since then, but I just haven't attempted to fix what isn't broke with JFS
JFS is NOT
actively developed, but it is maintained, with responses to bugs and other problems in less than 24 hours from IBM's devs.
I've read this issue with XFS, you would want to investigate to see if this issue is still present -
The use of XFS file systems on LVM2 logical volumes can cause system freezes under Linux based operating systems if the kernel is compiled with option CONFIG_4KSTACKS enabled. This happens when the system is under high disk I/O and require more than 4kB of thread stack.