I use emacs for nearly all my editing and interactive analysis. As one typically does, more than one project is the norm, not the exception. Discovering projectile for project-specific buffers and controls, combined with helm for very fast, fuzzy completions, makes emacs a very convenient and efficient environment for most task.
One challenge I ran into was the need to have multiple interactive python buffers, typically one per project. However, the out-of-the-box behavior of python-mode is to have only one python interactive buffer named “Python”.