Thirty-one authors and publishers tell their tips and tricks for publishing with Smashwords at the official Smashwords blog. These were all written in response to a call on the blog for posts on the authors' and publishers' own sites about their experiences with Smashwords.
I've read nine of the blogposts so far and they have been helpful. I've learned a couple of things I didn't know about formatting for Smashwords.
If you still haven't decided whether or not to use Smashwords, reading Smashwords: How to Self-Publish an Ebook with Smashwords: 31 ...may provide the help you need to make a decision.