I am using a new IBM T40 now as my main computer. I was about to go for the X31 which is lighter and smaller, but I have gotten used to the large resolution from my old T30.
Michael Zucchi provided me with a few links to people running Linux on the T40. Most hardware is supported on the T40, but the speed of the hard drive left much to be desired. The new T40 felt like it could not handle the load the T30 did. Any IO would make the system very slow.
After dropping by the #kernel channel on LinuxNet, I was told to upgrade my Kernel to the latest RH update. So far the speed of my hard drive went from 2.5 MB/second to 25 Mb/second. An e-mail expunge that used to take about two minutes seconds, now takes 13 seconds.