Good post, a few inaccuracies:

- cua0: the first serial port
The cu? devices are now deprecated in favour of /dev/tts/*

http://www.ibiblio.org/mdw/HOWTO/Serial-HOWTO-12.html

- random: a device that returns a random number
Or rather an indefinite stream of random junk

The /dev/ tutorial could also have used the devfs standards for device naming, which are beginning to supercede the "old" names for things. Simple devices (null, zero, random, full etc) stay the same - almost everything else is moved into a subdirectory of /dev

An extfs2 filesystem does not constantly bring the disk-index up to date (in opposition to DOS).
Not a feature fo the ext2fs, but rather any filesystem when mounted without the sync option under Linux. Also (confusingly) true of DOS filesystems mounted under Linux.