At yesterday's LOSUG Darren Moffat, Sun Senior Staff Engineer presented current status of ZFS encryption. It was really interesting presentation. He even managed to panic system :)
The good thing is it's going to be very easy to use and is going to be integrated relatively soon - IIRC about build 92. It was also nice to be able to talk to him after his presentation and share some thoughts.
If you are from London area I think it would be worthwhile to pop-in at LOSUG meeting - you can always learn something new or meet new people.