It is not 100% related but I have a premium whiteboard application on Chrome Web Store for $3.99. The volume is relatively small in comparison to folks at Apple App Store, I assume it's because many people barely know about Chrome Web Store yet. My sales figures: http://ohboard.com/blog/10-sales-in-2-weeks/
Though, I suggest you adding your web app to Chrome Web Store since it will not take you more than few hours and it will bring you users straight.
Shopify = Well worth it. A significant amount of new signups come from Shopify. Great support & communication.
Google Enterprise = Not worth it, whatsoever. The process is horrible (it took quite a while to understand the issues for denial because of the template answers). Definitely a - ROI for us.
Are you marketing your webapp in an app store (Google Chrome, Mozilla)? What are your results, lessons learned, and how has your experience been? Is it worth it, and should the rest of us consider doing this?
Though, I suggest you adding your web app to Chrome Web Store since it will not take you more than few hours and it will bring you users straight.