o	building root file systems from the source tree
	   o	installing kernels when cross compiling

These are only true if you're cross-compiling from a different
platform.  There is only one case I can think of where cross-compiling
for a system that isn't already running is even desirable, and that's
when someone is doing an initial port to a new machine.  In that case,
I would strongly encourage getting the machine to mount root over a
network interface first.  (This is partially because network drivers
are easier to write, and it means the rest of the port will get tested
sooner.)

	   o	(for x86) creating boot disks  (do you
		   really do everything on a disk then
		   DD it into a file?)

We use `vnd' devices for this, though mounting directly from a file is
probably more desirable.