Basic installation of Debian Lenny was no problem, although I didn’t try to configure the “special” hardware components (touch screen, built-in camera, wifi, etc.). The internal 128 GB SSD worked like a charm, thought.
I installed Lenny from a USB memory stick, downloading most of the system via network (using Ethernet, which works our of the box). I just followed instructions in Installing Debian GNU/Linux via the Internet (“Tiny CDs, floppy disks, USB sticks, etc” section). After reboot, I get a desktop, and the fundamental components seem to run. WIFI is one which is not working, and according to Installing Debian 5.0 (Lenny) on a ThinkPad X200, you need a customized kernel to make it work. Touchscreen is also not working, but I don’t even try to configure it.
I’m installing Lenny just to upgrade to testing (Squeeze), so I stop here in trying to configure Lenny, and move to upgrade to Squeeze, which is what I will try to configure to work with all the X200 hardware.