It appears if you create a product, and give it a SKU. Then search for the product using WP's search feature, the item is not found.
It would be favorable to be able to search by the SKU, for people looking for items by SKU.
Our current workaround is to add the SKU to the product Title, but that gets added to the invoices, etc. and looks messy.
Of course, this could just be a bug with our setup/theme (simplemarket), in which case, please do let me know that.