I have nothing new to post here on installation procedure. It has already been well documented and maintained by http://www.cyrius.com/debian/kirkwood/qnap/ts-119/install.html. I just follwed the steps given and got it installed successfully. I installed Debian 6.0 Squeeze (Testing) version.
blackgod@blackbox:~$ uname -aLinux blackbox 2.6.32-5-kirkwood #1 Sat Jul 24 13:37:14 UTC 2010 armv5tel GNU/Linux