Hey there, sorry for the slow reply, didn't notice it :) Yes, Debian is one of the most popular Linux distributions.
It's a fairly straightforward install, since aside from the lack of built-in keyboard and addition of digitizer it's a fairly typical laptop. It picked right up just about everything. I did install the gatos drivers for the video rather than the built-in X drivers to give me enhanced video support, you can see them http://gatos.sourceforge.net/ . Despite it talking about TV-Out and such which isn't relevant to our applications, The ati.2 does help. I don't know if the 3400 has the same graphics as the 3500 or not, the 3500 has an ATI Rage Mobility P/M.
Then from there I went to www.linuxslate.com and installed the proper pen driver, which worked without any extra config. I wish the source were available or the author would release a version with calibration support, it's not too bad but it's off enough to be annoying to scroll scrollbars and accurately click things sometimes. I may try the entries from the 2300 driver anyway and see if they do anything.
I've since recompiled kernel 2.6.4 for specific support of stuff, and it works great. Sound works well with ALSA, PC Cards are picked up no problem, on-board NIC and modem work great, I can watch videos and play quite a few games on it (even some DirectX stuff in Windows like Homeworld and Homeworld: Cataclysm. I do still have Win2k on there but rarely use it) and all in all I love this thing :) I still get a lot of comment on it when I have it with me places as there are a lot of people who still haven't heard of or seen a tablet PC.