Item: Magento Open Source
Rating: 8
Author: Santiago Valdés

Use Cases and Deployment Scope

We used Magento as an eCommerce solution for our company. We sell lots of different products, so scalability was an issue and we were recommended to use Magento. We didn't use it as fulfillment, only for processing orders and everything else was done outside of it. We published products from an API outside the store too.

Pros and Cons

Magento scales very well. That means if you keep adding more products, there's no significant performance decline. This sounds like a very technical and unuseful thing but actually it's very important and depends heavily on the type of eCommerce solution you are providing. In our case, we were supposed to have many products (+15,000) so we never have many scale issues with it.
Exporting information works reasonably well. It is relatively fast and has decent built-in capabilities.
Attributes are well built considering other eCommerce options. It's very flexible and you can modify many things, including brands, easily.
Multistore (differente languages/places) seems to work fine but we didn't use it. I'm just referring to what I've read

The community around Magento is very poor compared to other software. We migrated to WooCommerce and definitely there's more support there. More plugins, extensions, developers, etc., and at a reasonable price. This is one of the key points why we migrated. Magento is very expensive and slow to develop here. For WooCommerce there are plugins for everything, from popular analytics software to loyalty. This is a HUGE point to consider.
Debugging is painful. Some times you get an error that shut downs your entire store, and why did it happen? No clue. There's no documentation, there are 20,000+ files and at least for us, the framework on which it is built is not that user-friendly. This is expensive and there are not that many options compared to other software.
Changing the design or making changes is also very hard, because of the framework, the many files, and how complex Magento is.

Return on Investment

It definitely let us start with a decent store and scale from 0 to 15,000 products without many performance issues. But that comes with a cost: we were unable to change the design of the checkout, SEO was poor, and adding banners or more store-related things was very time consuming.
Debugging is hard and you will break your head with some errors that break your store, and you don't know how to solve them. This was one of the reasons why we left it.

Alternatives Considered

WooCommerce, PrestaShop and Shopify

In a few words:

WooCommerce: easy to setup, huge community and easy to customize. Hard to scale, but can be done.
PrestaShop: poor brother of WooCommerce. Less community, less customization... not sure why anybody would use it.
Shopify: SaaS solution. Harder to customize (due to Shopify restrictions) but very easy to setup and has many nice add-ons. Hard to manage at scale.
Magento: good at scaling, expensive to customize and in general to develop. Hard to customize.

Other Software Used

PrestaShop, Dropbox, Adobe Illustrator CC, Adobe Photoshop, Microsoft Office 2016

Likelihood to Recommend

Magento is good for stores that have high volumes of traffic and lots of products (20,000+). Also stores that are in many countries or need to have different stores but with the same stock.

Beware that the road will be painful: expensive developers (and not that many), little support or documentation, and hard to change the design to suit what you want to do. If you want to start a small store without many problems and don't have much budget, just go with WooCommerce. It's easy, fast and works pretty well for basic stuff (we had to invest some in scaling it, but now it works great.)

Scalable but expensive to customize

Overall Satisfaction with Magento Open Source (formerly Community Edition)