Open Cart has many pros to be the chosen CMS to develop a web project online sales, of someone who needs a quick solution, simple and does not require customizations to future functionality.
It is easy to install and configure, so basic pitch a web with simple categories, is a matter of minutes. Managing institutional pages is very simple and is also setting standards payment gateways.
Regarding the visuals, there are themes that meet basic needs quite well in a store and there are some other themes that are of a payment, which play a more refined level of expectation.
However, Open Cart is just exactly what mentioned. If you want more, then Open Cart becomes somewhat limited and incomplete.
Any nontraditional functionality becomes somewhat complicated, either because it must be done from the code (eg add a button on the main menu) or because it is required to do a special module (show a certain "view" of products in the home). There is no way to integrate content with products, in fact there is almost no possibility of creating an agile content. Nor can we set different types of "blocks" or clip art or any plugin that requires a customization point, without having severe headaches.
Regarding users establish functionalities linked to have a platform that provides poor different levels of access, unless manually develop in the modules required which is cumbersome and expensive.
Open Cart also doesn´t includes the possibility of making "views" that takes into account certain products that share relationships together.
The possibility of a make a custom theming is limited to the extent that we doesn´t have a highly developed community task doomed to refine methodologies for the task.
In conclusion we can assume that Open Cart can be good to set up a shop selling online simple, fast and scalable bit like solving something soon. If you need something just a little more complex, then Open Cart surely not be our solution.