Lock down which project is using which Ruby gems, on which versions, with Bundler! Gem versions can be a pain to manage, especially if you or your team members work on multiple projects simultaneously, or if you work with contractors, temps, etc. Case in point: projects stall, people leave, and hand-offs often don’t include robust documentation.
Using Bundler is a great practice if you aren’t going to be working on a project forever and someone else will have to pick up where you left off, if you are working on one legacy project and one bleeding edge project, or if you frequently come back to projects after not working on them for some amount of time. Additionally, it can be difficult to get the right gems (dependencies on specific versions) if you have multiple versions on your system. Setting up, managing, and updating your ruby gem environment is a tedious task. Bundler can help!