> switch to another branch, the files will still be in your working copy but not listed in your .gitignore file
This is a failing of git, imo. There should be a .local.gitignore to somesuch, that is "added to" .gitignore. It's VERY common for me to have files that I want ignore, but are specific to me; they don't belong in the project's .gitignore. I know there are ways to do this, but all of them are clunky. There should be a simple, out of the box way to do it.