MacOS – What are the options for full system (or at least home directory) encryption

You want to set an Open Firmware Password. This makes it so that a thief needs a password to boot to another disk (or do anything other than a normal boot). This means that they can't reset your password from the OS disc and get in anyway. This is an important security measure to take. The only problem is that you can't do things like safe boots and verbose mode. Here is an article about how to set up the OF password (and how to reset a user password).

And here is a general article about physical and virtual options to increase security (ways to help locate a stolen Mac, make thieves think it's broken, or even just lock it to your desk).

Your question contains the most important thing needed to secure a computer against a motivated attack to compromise a FileVault 2 protected Mac volume.

1. Don't connect FireWire to a device you don't or can't trust while you are logged in to an account that has file vault keys active.
2. Pick good single use passwords to reduce the chance of other compromises degrading the security of your FileVault password.
3. Update to 10.7.3 and verify sudo pmset -a destroyfvkeyonstandby 1 hibernatemode 25 power management settings that force hibernate mode to secure your keys from compromise when the device would normally "sleep"

I do follow Rich Trouton to keep up to date on his blog for nice commentary on securing macs. The mix of up to date topics seasoned with experience as a real world system administrator make his writing very valuable to me.

The crux of the issue is your parsing What user behavior is necessary to have security. I always like to think of security as a mindset and ongoing attempt to plan, implement, measure and adapt. Security isn't something you buy or something you "set up" and training users to actually not divulge the passcode they have used to store their unlock phrase is the weakest part of FileVault's security layer. Not reusing that passcode - having a system where you get your users to understand why their keychain password needs to be unique and secure is far, far harder and takes far longer than just setting up a plan for implementing file vault initially. Best of luck in your quest for security!