Sun have done some work in recent times with liveupgrade - the last time I looked at it, a few years back now, it was rubbish. I thought it was about time I took another look, since a lot of the updates in OpenSolaris were looking good.
This is one of the weirdest problems I’ve had for a while. On one of the servers I look after, my home directory was a zfs filesystem set to /home/user. If I ever did an rm -rf on a directory structure underneath my home dir, it would remove all the files but leave all directories in place. The only way to get rid of the directories was to recursively remove each one. Painful. Today I discovered a fix - although I don’t know the reason why.