I'm just in the process of trying to get Gentoo running happily onn an X300 with mediabase (with CDRW). I found that you have to use the modified DSDT file to get the acpi events working (acpi.sourceforge.net) (see the big DSDT and ACPI thread for instructions on how to do this:
http://forums.gentoo.org/viewtopic.php?t=122145
However, although the acpi stuff starts working when this is used, and I can do speedstepping etc, the docking station suddenly stops working. If you undock from the mediabase, the laptop hangs, with no obvious cause (I have tried stopping all services/removing modules prior to undock).
I also can't seem to get the laptop to detect the docking station if it is connected when it has been booted without it being present.
If anyone has any ideas, please let me know - otherwise the decision is whether to run with a working docking station (but no power management) or with power management (but no docking station)
(As an aside - for the 2.6(.1) kernel, neither of the inbuilt suspend-to-disk systems work - in the end I had to download and manually patch with the system at
http://swsusp.sourceforge.net (swsusp2) - as I also did when testing vanilla 2.4.24 - this works fine).