Beka Rice has done an awesome write-up on SellWithWP, where she analyzes who is using what WordPress eCommerce plugins out in the wild.
Not too surprisingly, WooCommerce is dominate, with over three quarters of marketshare, according to Builtwith. But the real fun comes when she excludes that. It shows that WP eCommerce still holds pretty strong, and Easy Digital Downloads is a serious player. It also shows just how small Jigoshop seemingly is. A couple of the plugins that register in the stats I haven't even heard of, or at least though of in years.
Of course, these stats may not be 100% accurate, as Beka notes. But this post is fun for you other data-nerds.