Tried this on debian 6 and ran in to limitations on the penmount side. Their latest driver did not include evtest although the readme indicated it was included. The result was that their driver did not report to the linux input layer. IE /dev/input/eventX. This is exactly what tslib needs to be able to work. After reporting this to their driver team they sent me a small package, including source, which has a small script that should work with the repository and their own penmount driver package.
I must have exchanged 30 emails with them since starting a debian 6 build. The end result, although not clearly proven yet, is that their drivers MAY not be i586 compatible. So we have been working on a way to get the penmount kernel driver to work on tslib instead of their gCal utility.
I was hoping to update this thread with a how to but I have just not gotten that far as of yet. Seems life threw me a curve ball recently and I went through an eviction last week. Staying in a temporary situation currently and all my tablets / electronics are in a self storage unit. If you want to give it a shot let me know, I can send you some copied instructions from the masses of emails as well as the script that I recently received to get the penmount kernel driver to report to the input layer. tslib is tiny in size so I am really hopeful that this will work. All attempts (even ubuntu and other drivers) I have made after my initial debian 6 build have not resulted well so this is pretty important to get functioning.