Sorry, I've updated my documentation. The ordinary post category column should be 'category' in most installs. My documentation was from before I added support for custom taxonomies which makes things a bit more complicated.
While this was the fault of my documentation, I highly recommend the quick start guide. By doing a small export first, and using the generated file as a template, you'll likely save yourself a headache or two. The plugin is designed to let WP/Excel do the heavy lifting, so the export first step is often crucial to get accurate field names and field order.
Hope that helps. Let me know how you go.