Security analysis of Full disk encryption?

Has anyone done a security analysis of full disk encryption under Lion?

I'm debating switching to it but I want to know more about how it works before I start trusting it to keep my data private. Anyone know if it now releases the encryption keys when the machine is in standby as FileVault in SL left everything unlocked in this state...

I did find a way to convert external drives to use encryption without formatting them assuming they are set up with a GDI partiton scheme: http://www.joshkerr.com/2011/06/using-file-vault-2-with-multiple-drives/