The new apostrophe-pieces-import module imports pieces from CSV files. There is a progress display, it’s possible to cancel the operation, and it’s easy to override the behavior in various ways. This will really speed your work when you have a large amount of existing content to pull in.
Out of the box, CSV and TSV files are supported. In addition, you can register new formats as long as you provide a Node.js stream that can read them and a few other odds and ends. And it’s possible to package up support for another format as an npm module for everyone. Check out the documentation for more information.