I have been working with eZ Publish for almost 10 years since 2005 beginning with eZ Publish 3.6.1.
In Europe this product is well known and use by a lot of company.
I really like this CMS not only because I know it very well technically but because it’s clearly more than just a CMS.
eZ Publish is a platform, it’s a CMF, a CMS and a CXM
I don't want to list all the good features provided by eZ Publish out of the box (content structure, flexibility, multilingualism, multi channels and so on) you should try! There are a lot and moreover it's very simple to extend the system yourself. (or add professional extension)
For me the most important thing I noticed over the years about eZ Publish and eZ Systems is their professionalism.
The backward compatibility has been maintained at least since 3.6.x. (yes! For almost over 10 years you can preserve your content in the database!)
That’s for me one of the most important thing I like in eZ. That’s what customers like and need!
eZ Publish is a platform adapted for professional projects. And professionals build non short-lived projects, they want to get something stable, scalable and able to evolve.
The second thing I like is the quality of the product under the hood. Everything is unit tested, it’s really clean, the source code respects a lot of web standards and that’s managed by teams of engineers completely committed to deliver a really good product.
It's a OpenSource project but eZ Teams valid, fix, improve community contributions and they assure the quality of the product.
Last point, because eZ Publish 3.x has suffered about some bad reputation : You can build high performance website with eZ Publish.
I have built with our team some very highly available websites on eZ Publish. Websites able to handle the traffic generated by (for example) the FIFA World Cup on a famous nationwide (France) newspaper website.
I dislike the Administration Interface. The first thing we do when we start a project: we change the CSS, add some icons to turn the Administration Interface more “user-friendly” for customers and contributors.
But I know eZ Systems are working on a new User Interface really interesting.
Since eZ Publish is based on Symfony2 there are many new possibilities. The community is now bigger than ever with the Symfony community.
My recommandation would be to test the product and think about eZ Publish like a platform and not just like a CMS.
There are a lot of concept behind eZ Publish, so it could appear to be a complex product. That’s true! But it’s a complex product able to lead you to what you want to.
Moreover there is a Support, an Enterprise Edition and very good consultants provided by eZ Systems.
But also Web Agencies able to help you on your projects ;-)