With regards to powering off, my desktop *does* power off. As far as distributions go, it's either hit or miss. In Slackware it doesn't, but in Knoppix, it does.

It all depends, too, on the motherboard. MS was given access to the "proper" method of powering off by all the various manufacturers, which is why it works for them (unless Windows crashes). The Linux people have had to reverse-engineer it, so it doesn't work in all cases.

AFAICT, motherboards only use either APM, or ACPI. Don't quote me on that, though.
My motherboard (Asus K7V333) uses APM, which Knoppix happens to use, but when I try to run a kernel with ACPI, it'll hang my PC.

I noticed as well that in LILO (/etc/lilo.conf) there's an append flag (that I can't remember) that contains "apm" and "power-off".