I can't provide citation about a thing that doesn't happen - you don't=20
hear things like "oh and yesterday I ran rsync on my Solaris with ZFS=20
and *it didn't crash*!" often.
But, with some grains of salt taken, consider this Google results:
* searching for "rsync crash solaris zfs": 790 results, most of them=20
obviously irrelevant
* searching for "rsync crash freebsd zfs": 10,800 results; a small=20
number of the results is from this thread, some are duplicates, but it's =
a large number in any case.
I feel that the number of Solaris+ZFS installations worldwide is larger=20
than that of FreeBSD+ZFS and they've had ZFS longer.