The Thecus n2100 is a pretty sweet machine. I'm pleased with it already. It can really run debian! I also have an NSLU2 which I've installed Debian on as well.
The Thecus I have came with a 9-pin console port which I was able to connect to (thank goodness!), and then I was able to see what I did wrong when following the install instructions. This was actually a really amazing process for me - I've connected to a Cisco switch via minicom, but never another linux machine. I'm sure this will come in handy again soon.
Here's the links I collected in researching the n2100:
My mistake: not changing the hostname on the thecus before installing the installer!
http://alcopop.org/log/debian/ - this page mentions the process for using a raid on the thecus with debian, you need the kernel modules. Unfortunately the udebs have advanced past the binary kernel version available from the debian team.