I like the plugin but the default invoice template sucks extremely.
So I decided to write down my own template.
Just drop the php file in /wp-content/plugins/woocommerce-pip/woocommerce-pip-template
and the css in /wp-content/plugins/woocommerce-pip/woocommerce-pip-template/css
It looks like this:
If you like it, post something above so we will keep it up for newcomers.
If you have problems let me know, we could fix things together.