I saw it near the end of previews and can't really remember very much about it. The music was passable in an over-the-top popera kind of way (helped by Jonathan Tunick's orchestrations which were fantastic as always) but, as you say, the lyrics were terrible. It was directed by Francesca Zambello - the staging was stunning (I seem to remember they had a hydrolic stage?) and it looked fantastic with lots of drapes and stuff, but as a show it just kind of lumbered along and you never really gave a toss what happened. It did star American-Broadway Anastasia Barzee along with Paul Baker and Uwe Kroger alternating in the title role (I saw the former and he seemed a little lost) and a wonderfully over the top performance from David Burt as Talleyrand. Apparently a complete 'soundboard' recording was made near the end of the run and was intended for release, but it never happened.
Of all the many flop musicals to open in 2000 (The Beautiful Game, Witches of Eastwick, La Cava, Napoleon, Lautrec, Notre Dame de Paris) this was one of the most boring (IMO, naturally!).
There are production images on Francesca Zambello's website, below.
http://www.francescazambello.com/gallery/napoleon.html