I went through a bit of trouble installing Xubuntu Feisty Fawn onto my Thinkpad t22 laptop today. The install went off without a hitch onto my desktop PC, but I got one “corrupt package” error after another during the extraction of the base installation files onto the laptop. Perhaps something is wrong with the cd/dvd drive?
As a rather kludgy work-around, I reinstalled a command-line system of Xubuntu Edgy Eft, changed the apt-sources list file to look for Feisty sources, upgraded the command-line system to Feisty, and then installed the Feisty xubuntu-desktop metapackage. That went off without a hitch. I was even able to get wifi up and running after installing linux kernel restricted modules. I obtained the nifty instructions on how to do so from here. As I say, “nifty.”
With a nice install of xubuntu, I’ll now be able to continue on w/ my xubuntu-doc bug reporting, which is off to a decent start. 
I saw you filed a bug reports about xubuntu feisty, good job. As a general rule, I point my sources to the next release cycle, I know nixternal does as well.
I meant editing your /etc/apt/sources.list from edgy to feisty. I do that with all my systems when I update to the latest release.