For quite a few years, we have used osCommerce and ZenCart for our e-commerce solutions. However, with our switch to using Joomla as the base for client websites, we have now switched to Hikashop.
Something that is a very serious issue for our clients is the ability for customers to get a shipping cost estimate prior to registering. In both OSC and ZC, it is a simple function when you go to the shopping cart. You click a link to bring up a pop-up, enter your zip or postal code, and any valid shipping methods/options (activated modules) are listed with prices.
It can be VERY difficult to get an online customer to buy when they cannot get an estimate of the shipping cost. Some online merchants overcharge for shipping. And many customers do not want you to have their info until they are ready to commit to buying (which they don't want to do until they know the entire price of the transaction).
I have read other threads that have discussed this issue, so I understand there are others who need this. I know our clients will lose business in the short term with their new Hikashop carts due to this issue (they sell competitive online products), so I hope this is something that I can tell them you are working on to resolve. Keep up the good work. Thanks.