Early 2013 is where it all began. Coming from a full backend CMS, using concrete5 was quite the difference. Don't forget, we can still manage items (pages, members, etc.) in the backend (and more if we'd like to). So that makes this CMS quite complete. Now version 5.7.x is stable, more and more users are using this new version. Not only did they update it to current coding standards, but also made some UI/UX changes. It was a bit hard coming from version 5.6.x, but once you are used to it, you will simply love it. If you are still on 5.6, please invest some time in 5.7. You will not regret it for a single second (at least, I hope you won't..).
There are 11 Add-Ons in the concrete5 marketplace right now, developed by me (username ramonleenders). All-time-favourite would be Block Designer (most 5.6 users will remember "Designer Content", which is a lot alike). More Add-Ons will be coming and its quality will be the same as you are used to with the current Add-Ons from me. I'm also planning on making themes with Bootstrap, Sass and a lot of nice pages/page types.
I hope I will be contributing to the concrete5 marketplace more and more and make concrete5 a bigger and better solution for content editors, developers and all the fans around the world. It's already a super duper awesome CMS, so better start using it if you aren't already!