Hmmm… with OS X Lion having full disk encryption as standard functionality, I'd posit that's a much better way to go, now that you've revived a thread that's been dead for 2 years ;-)
Full disk encryption is only part of securing your data and I do have my OmniFocus DB on an enrypted image that opens up on login. I also made sure to kill the location where OmniFocus performs it's automatic backups and I have procedures in place to ensure that I don't sync plaintext data because my webdav server stores an unencrypted version of the OmniFocus DB (to be fixed eventually) and I also make sure that I don't accidentally have Time Machine run a backup while I'm working with plaintext that should otherwise be encrypted.
Not to mention, since you can only have one OmniFocus DB sync to your iPod or iPhone at a time and if you don't want to use a different scheme to track your projects and next actions, then you require partial encryption mostly to have your projects still be in OmniFocus all the while not being available for the whole world to see on your iPod or even on your computer (either accidentally or intentionally via theft, hack, shoulder-surfing, etc.). The partial encryption performed via the script solves the problem and lets you work your projects and tasks when it's secure whereas full disk encryption simply doesn't address the problem all the while doing so on the wrong device :).
There is a downside in that you can't get access to your encrypted data easily on your iPod (I may fix this someday) but I'm okay living with that and only handling the more sensitive items on my computer.
Last edited by omniinmo; 2011-10-26 at 01:50 PM..