I'm a bit biased since I'm one of the very few Kentico Partners who only implements Kentico and no other CMS solution like SiteCore, DotNetNuke, WordPress, Drupal, etc.
I've worked with other CMS software solutions previously and by far this has been the easiest to setup, implement, develop against and maintain. In the 8 years I've been working with Kentico, the stability of the product has just gotten better.
The API could use a little work but overall it is very simple to work with. In just the last major upgrade many changes were made to make the API much easier to work with and more standard. I've implemented websites with other systems and have not had any kind of issues with the Kentico API's not working as expected.
Hotfixes are released every Friday morning. The key to bug fixes is that the bug has to be in the actual Kentico code and reproducible by the development team at Kentico. Once they can replicate the issue you've reported, it will be fixed within 7 business days. Most software companies hide the fact that there are mistakes or bugs, Kentico essentially challenges people to find them.
See more here:
Trees for Bugs
Overall Kentico is a very robust solution and if you'd like more information or comparison or sales information, please reach out. You might also check out the Kentico Connections conference coming up this fall.
Best of luck!