I've run into problems bind-mounting node_modules, so I just do an install for the image. There are the performance problems you mentioned, but also sometimes libraries build differently in Linux vs. Mac.
Yes, we no longer bind-mount node_modules or bundled gems, but I still run into a lot of performance issues with Docker generally (especially very high kernel CPU usage). Additionally, not having node_modules and bundled gems accessible from my development environment makes it harder to diagnose dependency issues when I need to (e.g. pull up the source code for a gem and see why it's not working).
