My account validation email was never sent, but after a few days I could go ahead and just login to iTunes Connect.
My book review cycle took 7 days and 3 iterations. Mostly no links to YouTube videos (instead included videos only) and no links to books on Amazon. Photos and videos are big part of my cycling and climbing adventure book. Including all ten 5min videos would have bloated the iBook by about 1GB, leaving them out wouldn't be good either. So I decided to include abbreviated 1min versions of each, with a link to my companion website for the full versions. Check it out:
http://itunes.apple.com/us/book/panamerican-peaks/id533289640
Response time was usually next day, once 4 days over weekend. Not stellar, but ok.
Bottom line: Store support (for authors) is poor, but the iBooks Author tool and the iBook reading experience on the iPad is great! And that's the only thing that matters in the end.