Here's a link to a great article by Kristine Kathryn Rusch. One of the most interesting things in it, for me at least, is the comparison of "new" and "old" publishing, and the idea that writers accustomed to traditional publishing don't often recognize what success looks like in self-publishing. She writes:
In the old [world of publishing], books had to sell fast because they’d be off the shelf in three months (or less). In the new, the book is just starting to get noticed a year after publication. It might have its best sales month 29 months after publication.
If you're interested in publishing, I highly recommend you read the rest of the article.