I like how it has the ability to have multiple users working in one project so if someone leaves you're not stuck with their work and also allows for more than one person to be involved in the same project which makes things easier.
I dislike how there isn't any way to have a sub-project within an existing project. This can get confusing when you are trying to move forward with your tasks and projects. For example, I am currently using it to organize my day-to-day tasks and projects and then having it linked up with our office Project Management tool.