Seems like there's little to gain and a lot to configure/worry about with the Docker setup. Happy to be learned somethin' ... just would like to know what that somethin' is.
* You can run different versions of program side-by-side: FF 32 in one window, and FF 31 in another to test compatibility and regression.
* You can install programs without polluting your base system. I don't want to have Java installed, but sometimes I just need to run an applet.
All of that can be achieved with traditional VM, but with the performance penalty. As Docker runs on top of the native kernel, speed should be comparable to the application running directly on host.
In a traditional VM, you have to reserve memory that is used by the guest OS and the apps you want to run, and is unavailable as soon as the VM comes up.
Docker is incredibly lightweight in comparison. Also, you can move your development environment around, same way you would move a VM disk around. That requires less resources, again, as there is no OS install.