Shortcodes are too complicated for a non-computer-savvy client.
If I could change any two things for WooCommerce (more like if I had the time) without straying away from what it's "designed for", I would (1) make the Kitchen Sink shortcode button have more of a GUI for selecting things so ID numbers or SKU codes don't need to be remembered/copied/pasted but inserted directly, and (2) change the "Select options" button generated by the shortcode for variable products to an actual option selection dropdown menu to avoid the user having to leave the page just to select product options.
For those two reasons (and that's really all) I cannot use WooCommerce on my current project despite how nice it is. :(