FWIW, my rule of thumb is that if it's not a job for a text editor
(NoteTab Light or Notepad++ on Windows, GEdit on Ubuntu), and it's not a
letter, then it's a job for LyX. The only reason I don't use LyX for
letters is that our office stationary has boilerplate in both the top
margin and the left margin, and I've yet to see a LaTeX class that would
accommodate both. So I keep a rusty copy of WordPerfect around for that
(and for opening old WP files, of course).
I haven't tried typing math in Open Office, but the math editors in both
Word and WP would drive me nuts at this point. Most of the time in LyX
I'm doing an article, a presentation or something like a syllabus, but
I've moved my CV to LyX as well.
IMHO, LyX + Beamer is a tough act to beat for presentations,
particularly if you're putting in math.
My $0.02 (0.000000001 euros at current conversion rates).