The Major Thing Missing In Drupal Commerce
Documentation, hands down.
Honestly, I applaud the efforts of the Commerce Guys.
When I started working with Drupal Commerce last year, I was so excited by the prospect of a scalable e-commerce solution that could be tailored to my web development needs... after all, it had the power of Rules, right?
Only, building Commerce on Rules would be kind of like building Drupal Core on Views. Though very powerful, Views would actually be quite limited when handed the task to meet Drupal's demands. And so it is with Rules and Commerce. Things which should be simple to implement have now become quite complex and only achievable in a limited scope because Rules is limited.
And so the modules pile on and on as Drupalians find solutions and work-arounds, which is great for the originators of the code... but what about everybody else? We need documentation--sure, screencasts would be stellar, but a manual would import relief of biblical proportions.
And after tweeting this in frustration, I received a reply that full documentation is on the way. All Hail the Kings of Commerce? I certainly hope so.
Short-term request for the manual... define terms. I can't tell you how long it took me to discern the difference between a field, a line item and a component.
In the long term, it would be nice if Commerce came with a few more out-of-the box features, especially support for virtual product types like downloads, subscriptions, and the sell of user roles. And less dependence on Rules... or maybe user friendly Rules wizards that save time and sanity :P