I just used Prestashop for the first time and, although I only needed need two extra modules (only one of which was paid for and was just $20), I found it a pleasurable and fairly pain free experience, with quick and knowledgeable help from the forum for most of my questions. The only possible criticism about the forum was requests for answers to questions that had already been answered. Which is fair enough, that’s what the forum search facility is for.
I went with OpenCart after checking Magento and PrestaShop...
Magento is huge and geared towards the enterprise shopping experience,
PrestaShop is very nice but as you discovered, a lot of modules are
commercial and it uses Smarty. OpenCart is nice, all PHP but it
depends on one developer only, it is also quite a young project, so
we will have to keep an eye on it... when I have time I will
set up a store with OC.
Lately, there is ShopKeeper which looks very very good and also the
new version of TreasureChest which is commercial too...
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