Does anyone have any experience (good or bad) using Docker for developing a game with SDL and/or C++?

I can see it being useful for sharing the build environment, though games typically being compiled, GUI applications makes Docker seem like a bit more of a foreign concept.

What are you planning to put in the virtual environment?

If you have a distributed build system that goes to many machines then building a docker container can help distribute them.

If you have a data backend that needs replication it might make sense.

I have no experience of using Docker for games. I don't think it's a good fit, because the general idea is that everyone can work with an environment that is similar for development and deployment. You're not going to deploy Dockerfiles to end users.