I'm proud to be the owner of a HP Omnibook xe4400.
I think I don't need to insist on the fact that it's absolutely impossible to work with the supplied operating system (namely: Microsoft Windows XP).
It took no long (I didn't even boot it once) until I threw out all the partitions and installed Gentoo Linux. My favourite Linux distribution (Linux From Scratch) was not really suited as do a lot of testing on this machine.
As it was the first notebook I owned and the first time I made real use of ACPI, it was quite a struggle.
I want to share my experience so that others can benefit from it.
Prerequisits
Update to the lastest BIOS availiable.
The kernel
The use of a kernel of the 2.6 branch is highly recommended. The newer releases include a lot of patches to make Linux running on a notebook much smoother, although the processor ACPI module has proven to lock up the notebook since kernel 2.6.5, so just don't build it. If you want to check the temperature of your processor, go for the omnibook module of the omke project.
If you want to use your synaptics touchpad and an USB Mouse simultaneously you should consider to disable the Legacy USB in the BIOS. If loading Linux gets slow, add the compact option to LILO. Your touchpad will be available as /dev/input/mouse0 and the USB Mouse as /dev/input/mouse1.
Software suspend
Well, it used to work. But for what reason ever, the newer releases don't suspend the machine anymore. Instead, they either lock up or restore right after having suspended... I've no real use for suspension at the moment, but I'll look into that issue later on.
Who is this General Failure and why is he reading my disk?
It will be very unlikely that your notebook doesn't run any process you don't need.
And of these processes some will keep accessing your hard disk which is really anoying when you want to put the drive in sleep mode to: 1. Save power; 2. Keep your notebook quiet; 3. Work in peace.
Have a look at the quietlinux HOWTO to track down the processes.
More detailed and complementary informations yet to come...
"Wie durch farbige Brillenglaeser alle Dinge gefaerbt erscheinen, so faerbt ein selbstgerechtes Herz unser Tun, bis das Schlimmere als das Bessere und das Boese wie Gerechtigkeit aussieht." C. H. Spurgeon