Been using EP Advanced for a couple of years now. I absolutely love that software without it I won't have a business.

The buffer error only shows up when you tabs don't match the header, or you start on a column that is not column A in excel. Plus you have to include the EOREOR.

By far the EPA is one of the most user friendly none complicated Zen Cart tool. There are tons of documents barred inside the download for customization and explanation.

I think the problem lies in your excel (tab sheet) rather than the software itself. You can copy and paste value in a new excel sheet and try to run it again.

Or you can upload the tab file to the server (FTP) then import it into database. I can upload up to 5000 Products in one sheet.

EP does allow you to upload meta data, move products and categories, add categories and edit products based on product_id which i think the Free one doesn't do.