I later wondered if Google Play was worth looking into as an avenue for promoting my books and found a blog post that covers the process for self publishing an e-book with Google Play. The problem appears to be the discounting. Amazon will lower their price to whatever the lowest price you have your book listed for at other locations. If Google Play discounts your book price, then Amazon will follow suit. You can read the full blog post here. For now, I'll stick with Smashwords and Amazon.
Have you had any experience with Google Play? I'd be interested to hear your comments.