I have a very small tweak for you...
If you set up a custom product subtype as per the Satchmo docs, when create the main product record you will see some links at the bottom to add the sub type.
But the link uses the raw class name, rather than the 'pretty' version.
Just needs a small tweak to product/templatetags/satchmo_product_admin.py to fix this... patch file attached.
Seems to work ok, hope there's no issues I missed.