Well, I for one thing, will implement ePUB now in my book assembling and uploading process from now on.
Pagebreaks on chapters work fine now and TOC is ok, too. There are only a few rules I have to take attention to and ePUB generation via Calibre is relatively trivial via now (big cigar for Kovid!).
There are a few other reasons to make the jump now:
1. My daughter gifted me an Ipod Touch for Xmas
(tell you a secret: I make a lot of them books for my reading pleasure)
2. I think Sony and his reader will be relatively big in Germany this year, what with Kindle not present on the german market yet. So epub will be boosted (Libri.de, the biggest german bookstore chain, will sell the Sony 505 and epub ebooks in bookstores and online)
3. Bookeen will provide ePUB support in it's next firmware update (hopefully)