I admire the energy and devotion of the Lilypond developers. Also, the points they make about layout on their site are very perceptive.
Unfortunately, the example they published on Macupdate looks pretty bad as far as layout goes, with collisions and unevenness. It just doesn't seem to justify the steep learning curve.
As much as I am indifferent to the very complex music of Brian Ferneyhough, he uses Finale to typeset it. I imagine that it would be impossible for Lilypond to set even one bar of his music.
I've used iTeX with god results, but if you want to introduce non-programming friends to LaTeX/TeTeX, you need to look at LyX, reviewed here on 23 November. It runs on the same TeTeX base as does iTeX (G.Wierda's site there noted), but is basically a WYSIWYM (What You Mean) front for TeTEX. Very easy to use. Very configurable. Writing letter is even easier than with MS Word and they look a hell of a lot better as well. Just use 'Times' instead of the bitmapped Computer Modern and things look pretty smooth. Peter 232
I am a Free member 
LilyPond
Unfortunately, the example they published on Macupdate looks pretty bad as far as layout goes, with collisions and unevenness. It just doesn't seem to justify the steep learning curve.
As much as I am indifferent to the very complex music of Brian Ferneyhough, he uses Finale to typeset it. I imagine that it would be impossible for Lilypond to set even one bar of his music.
Good luck, anyway!
iTeXMac
LyX
If you read the 'Read Me', you will see instructions for TeTex at http://www.18james.com/lyx_on_aqua.html
It's a bit fiddly to get going, but once you've got the hang of it, there's no going back. And you can easily change the whole GUI langusge as well.