The first reference for installing debian on an Eee PC is The Debian Eee PC project. However it says on
its models page that it does not fully support 1201HA, because it uses the Poulsbo chipset. The reason is that it’s not supported by mainstream debian: see #533450 for details…

However installing debian Squeeze (testing) using the debian installer snapshot was fearly easy. Read DebianEeePC/HowTo/InstallUsingStandardInstaller for details.

The only noticeable issues I had was with partitioning where the partition table was not reloaded by the kernel; and grub that installed itself on my installation USB Key instead of the primary drive.

A good point is that network and wifi worked out of the box. So then I needed X to work with the native resolution.

Reading the above bugreport and a few other website showed that there are two drivers out there. One poulsbo driver (that seams to come from ubuntu) and the intel IEGD driver. Nobody seams to maintain the first one, and the second is proprietary but at least works. However none work with the 1.7 version of xserver. So the first step is to get an older xserver.

Lenny has and old one but downgrading all X related packages (including gnome ones) was a pain, so I quickly switched to an other solution:
Rebuilding and xserver 1.6 package.

See next post for details on building the xserver 1.6 packages.

This solution worked fine with the IEDG 10.3 driver.
I’m still experiencing some X freeze from time to time (which are solved only by rebooting). The touchpad does not have the multifinger features I was used to, and sometime the cursor jump to the lower right corner, but I didn’t really tried to investigate this anyway.

Update
As Steve McIntyre pointed out there is an other way to get the native resolution, using grub2 and fbdev, see http://wiki.debian.org/DebianEeePC/Model/1101HA for details.
I just updated to this configuration and it works !