It's not clear from the UI how to go about setting this up.

In particular, admin/settings/webform_associate/productize lets me pick a node type that isn't a product. Creating a node of this type then gives errors, price not stored, etc etc.

Two fixes needed:
- only show products at admin/settings/webform_associate/productize
- some basic documentation to explain the set up steps:
1. Create a new node type in UC product classes admin
2. Associate it to webform at admin/settings/webform_associate
3. Enable it at admin/settings/webform_associate/productize

assuming I've understood correctly ;)