[texhax] Omega

[Karl Berry]

    but did not follow it up then because it sounded somewhat too much in
    flux and neither sufficient documentation nor source were available

Omega (both source and binaries) have been included in TeX Live
(tug.org/texlive) for some years now.  How usable it is straight out of
the distribution is another matter.  (I have no experience with it.)

    Never heard of e-tex. 

It is a relatively conservative extension of tex done quite a few years
ago now, allowing for more registers (64k instead of 256), more tracing,
right-to-left typesetting, and other assorted nice (and uncontroversial,
as far as I know) features.  Version 2.2 will be released this year.

As of last year, the LaTeX team requested that etex be the default
engine for latex, and we made this so for TeX Live.

I think Robin answered most everything else.
(Robin: perhaps some of the above details would be worth including in
http://www.tex.ac.uk/cgi-bin/texfaq2html?label=NTS.)

Cheers,
karl