I almost never am able to "Look Inside" new pre-pubs anymore. I know it takes extra work to put up the preview excerpts, but please do that at the same time as you list each book on pre-pub. It's when they newly come out that they attract the most attention, and that's when people want to go browsing in them to see if they want to order them.
As it is now, some of us are jumping over to Amazon.com to check out the inside of the book, and if it costs less over there...well, you might just lose yourself a sale.