I had worked with PHP Nuke back in the day, so when I got in to ASP.Net sites I thought I would give DNN a try.  I pitched it to a client and set up a demo and the main thing I noticed was that DNN was way slow. And is was a drag to skin.  I abandoned it and went with something else. With Kentico I built and deployed a full blown municipal site with all the bells and whistles in 90 days. That included the time to gather all the info and requirements and have me and my intern put in the initial data. We trained municipal employees to keep it updated and the only time I get called is when they want to add some new feature.
We have built sites with all sorts of intergrations; intranets, ZenDesk, Jquery slideshows, Mootools plugins - we haven't found anything we couldn't do. The main weakness in Kentico is the E-commerce module. We had to write our own code for shipping by weight to work. Our programmer was able to look at the API and have this done  and tested in a couple of days.
In my world results count, and for me the results have spoken for themselves. We use Kentico all the time and are able to rapidly deploy high performance websites that will adapt to anything I design like clockwork.
BTW - I have done three sites for non-profits using the free license, I think you will find it quite capable. You can see two of  them at http://smithvillemusicfestival.org and  http://lostpinesartisansalliance.org.
I do use other codebases when Kentico is overkill. We have used wordpress and ModX for a couple of clients and for real simple stuff I use Surreal CMS.
I would recommend Kentico - here is my blog where you will find a tutorial on porting an html template into Kentico - http://leswarren.blogspot.com/2009/12/my-kentico-design-workflow-update.html
Contact me if you need any help.