These changes unfortunately mean WooTickets 1.0 is not fully compatible with WooCommerce 2.0 – and so our recommendation would be to avoid updating just yet if you wish to keep selling tickets.
We are currently testing a new version of WooTickets that is fully compatible with WooCommerce 2.0 and it is our number one priority to complete testing and release this as quickly as possible – so you shouldn’t have to wait too long. If anyone has any further questions about this please feel free to post them below.
I just upgraded as well (although in a sandbox) and had the same result. I was able to restore functionality by deactivating but [not deleting] wootickets, un-install WC 2.0.1 plugin and then re-install woo 1.6.6 found here, http://wordpress.org/extend/plugins/woocommerce/developers/ re-activate wootickets and you should up and running after a quick settings re-config… (takes notes of ALL your settings BEFORE deleting 2.01, and back-up just incase)
*no guarantees here so back up