I have tested "preseed - 1.71ubuntu1.1" by rebuilding the source code on a PPA along with d-i "20101020ubuntu451.6" in order to get a mini.iso.
I confirmed the mini.iso override the hostname as expected if "netcfg/hostname" is set and that the override occurred before the disk configuration for the vg name to match with the overridden hostname, if LVM is use.
I have tested "preseed - 1.71ubuntu1.1" by rebuilding the source code on a PPA along with d-i "20101020ubuntu 451.6" in order to get a mini.iso.
I confirmed the mini.iso override the hostname as expected if "netcfg/hostname" is set and that the override occurred before the disk configuration for the vg name to match with the overridden hostname, if LVM is use.
Eric