The security is the most valuable feature, in particular, the way I can give different access to different areas to different people, so you can really fine-tune access for different users.

It's completely no code, so I can build all of the logic in workflow tools. You can build quite complex business logic and business workflows.

You've also got nice filtering and exporting of data from the system.

The pricing model is very good.

When you want to extend or customize it, you can do so using JavaScript CSS, and HTML, so you're not limited to what you get from Knack.

It integrates well with Zapier, which is an integration toolset. This means that you can integrate it into other systems, as well. For example, I have integrated it with Google Sheets, Xero and most other cloud based business systems. 

I was also able to integrate with Google Single Sign On so that the client can manage access from their Gsuite Control Panel. This was very easy to do

The interface looks great.

Being a cloud-based product, I don't have to worry about infrastructure, backup, dev ops etc

Their written support documentation is excellent and I find their support very good.