I never had legacy FileVault eat my homedir, but I did have issues with it forgetting what program was supposed to be used to open what kinds of files. Very strange, that.
There was a workaround I had running for a while in a large deployment in the form of a logouthook that would copy the relevant prefs to a location that LaunchServices would find it before FileVault finished mounting the home directory.
There were a lot of corporate/education deployments running "legacy" FileVault who hadn't invested in PGP WDE or other commercial options, and I bet they haven't all upgraded instantly to the new FileVault when they moved to Lion.