I missed this post a couple of days ago, when Dean Wesley Smith posted about ebook sales at his blog.
Smith delves into the issue of ebook sales to the different ereaders: Nook, Kobo, Diesel, etc. Yes, there are more ereaders out there than the Kindle. You are limiting your sales potential by not seeking out these other formats.
Smith also addresses using Smashwords to get distribution of your ebooks into the other eretailers besides Amazon. If you invest the time to format your ebook to get it accepted into Smashwords Premium Catalog, it will be available to the other eretailers.
Increase your ebook sales with increased distribution using Dean Wesley Smith's tips.