Thanks for the two cents, Derek. Somewhere here on the forums is a discussion in progress about the ups and downs of projects like the Gutenburg Project, which unto itself is brilliant.
Generally, the discussion seems to revolve around two thoughts: 1.) Pro: we should have the Gutenbury Project, because it's free and there's lots of books there - at the very least, it's good for testing. 2.) Con: because the Gutenburg Project is only out-of-copyright books, returning these results will be of limited use to mainstream users - our focus is on matching the books you find when you walk into the bookstore or library.
If you can track down the thread, there's a fair amount of discussion on there about the issue. I think the thoughts - as of right now - are represented as a question (on which your input would be useful) and a statement.
1. If we included the Gutenburg Project in the system, would it actually increase your likelihood of using it to find new books to read?
2. Absolutely it's silly not to consider including the Gutenburg Project and similar free databases. We'll certainly consider including it once we have a better idea of how we're planning on moving forward (i.e. if we have any success courting larger, already established databases).
Hopefully that paraphrases the question accurately.

Aaron