On re-reading my note, I see that it sounds rather snarkier than I intended. Please accept my apologies for any negativity in that note.
As far as producing professional looking eBook, I've been having excellent luck starting from html and using html2lrf (part of kovidgoyal's libprs500). It does quite a nice job with minimal user intervention. The problem would be taking a book in one of the open formats that (say) Fictionwise sells and converting it into html without too much work. I've heard rumors that there's a convert-lit program that'll do that -- but I don't really know from my own experience.
Hope you find a good solution. And please let us know what you eventually work out!