I've installed a linux mandrake 10 on a 1681 yesterday :-)
the good :
No problem with partitionning.
the bad :
No acpi. The 1'st reboot hang on acpi. I have to boot the mdk cd in rescue mode and add 'acpi=ht' in lilo.conf, then restore lilo boot.
So, the notepad don't just down, you must press the button for 8 sec for it :-) And no sleep or hibernate of course.
It seem to be a pain to make that work !
Centrino wifi not detected.
Audio volume adjust with keyboard.
The 'not so bad' :
I've tried the ati linux driver (for 'made by ati cards'), and ... it works. After some tweaks to compile the new kernel module, etc... But anything impossible. Just read the help files from ati.
I own a thinkpad R40. Everything is supported under Linux, apm and hibernate also.. But the video card is simplest.
So, you choose :-)