Lightweight and Easy to look at
A client of mine used Cerri to track their projects. As someone who consults on contracts, it's not uncommon that clients ask me to use the tools that are native to their organization, but I've continued to use Cerri beyond my time at that organization because it's just so damn easy to use. I can track all my projects on a single screen with their dashboard and the tasks allow me to know what's due today, next week, and even months from now. Plus their file storage lets me share items without having to worry if the person has the right permissions for their Google Drive or Dropbox link.
When I was using it, I found that the knowledge base was slightly lacking, but looking at it now they seem to have revamped it recently.