I have used this HOWTO
to set up a keyfile for my encrypted home partition.
This work very well.
Now, I tried the same HOWTO for setting up a keyfile for my encrypted swap partition and that fails. I am still asked for the passphrase of the swap partition. That may be because the swap partition is mounted before the root partition. The keyfile is then not available, yet.
This my configuration.
I am using Ubuntu jaunty jackpole daily.