I have recently installed 2.4.22-pre4, after briefly testing
2.5.72 in the hopes of better battery life than 2.4.20.
I have found a couple of issues that I'm wondering about.
When compiling, it's only possible to build ACPI into the kernel.
If you then choose to build things (battery, ac adaptor) into modules,
they won't install.
On the flip-side, /proc/acpi/battery/BAT1/info now seems to change
based on the battery that is installed when it does not on 2.5.72.
echo 4 >/proc/acpi/sleep
seems to work much more reliably than it did under 2.5.72.
I have not (as of yet, about 10 suspends) had it fail to recover.
(I cannot test as much as I might like at the moment, the hard drive
is becoming erattic, and I need to swap it out.)