I have used this software for more than 3 years now, it is very stable so far! It's easy to use (especially if you are familiar with other products from Kovik).
The support team was helpful when needed in my case - they also were able to help me install an upgrade of the product that we had done before without any problems at all; which helped us avoid downtime during our migration project. There isn't anything bad about K3 as such but there might be some things worth looking into while using them like how their pricing model works or what kind of plans do exist etc., those can definitely make your life easier later down the line especially after working together many times over time. We need something reliable yet flexible enough because sometimes clients want changes within minutes/hours instead of days /weeks.