InVision is a tool that is great to present designs to your clients and communicate with them effectively. Before existing InVision, making a design proposal was a lot of effort: capture a jpg, send it, the client will pass it to PDF, make notes on that document to send it back with feedback All this process, which may sound like prehistory, is relatively recent. However, since InVision exists, you can directly upload the project you are doing, you can update it, and the client can leave comments on the same design.
Another thing that I love is that it allows you to order all your projects in a single screen, as a private portfolio to have everything perfectly organized.
A handy feature that InVision has is that it allows you to update the designs using the integrated Craft plugin in Sketch. Through the "inspect" tab of invision, frontends can access design styles and assets.
I also really like the boards as an inspiration tool, to make a quick portfolio or as a style guide so that the client can know colors, typographies, logos, etc.
The price, because if you are a freelance is a bit expensive and the free version only allows you to upload one project.
A feature called Freehand in which you can theoretically comment on a design with the client live via videoconference, but it has never worked well for me.
I would like the boards could be integrated with other applications like Pinterest or Instagram so that the process of uploading and storing images is easier.
Workflows, I do not use them because we have trello.