João Gomes:
Definitely the community. They develop the CMS and provided all the support I ever needed to climb the learning curve every time I needed to.

Jeremy Farrance:
Repeated project successes, the flexibility of the platform, and the very long term reliability!

Robin Hogg:
Easy to use and I've worked with it for so long I know it quite well. I also believe it is more secure than other solutions.

Tycho de Waard:
The very editor friendly CMS, the very reliable platform and the amazing community :-)
And: it takes at least 1 year, probably 2 to acquire the same level of skills and knowledge in a new platform. In money: it costs at least 100.000 euro to switch. I have been using other opensource products as well, like nopcommerce. But the community is virtually non existant. Learning gets really hard that way.

Simon Thompson:
The availability of external skins and functionality meant I could deliver all my clients needs in a consistent and logical way.

Ryan Moore & Moore Creative:
Having worked within different communities of CMS systems, from Mambo/Joomla, PHProjekt, SiteCore, Umbraco, and of course, including WordPress, I had never encountered before such a welcoming, helpful community of developers and community members using a platform together and helping each other with training, support and camaraderie. Ignoring all of the other completely sound technical reasons to continue using DNN for projects for the far foreseeable future, the DNN Community of users and developers is 100% reason to stick with DNN.