If Twitter could use common standard like microdata (proposed by w3c), it would probably be a better approach.
The big problem with Twitter product cards is the lack of real time information (ie the data shown to user is crawler dependent). So, e-commerce vendors with dynamic pricing needs (like hotels, airlines) wont use it much. E-Commerce vendors (like Etsy) where users are little less price sensitive have a better shot at using these cards.
This is a really straight forward explanation of how to implement cards in Twitter. Each social platform (Pinterest, FB, Goog Now, Twitter) requires a different implementation to achieve a similar goal. This is a good nuts and bolts view of what you need to do in Twitter to make it happen
The big problem with Twitter product cards is the lack of real time information (ie the data shown to user is crawler dependent). So, e-commerce vendors with dynamic pricing needs (like hotels, airlines) wont use it much. E-Commerce vendors (like Etsy) where users are little less price sensitive have a better shot at using these cards.