I have noticed that the "Only authenticated users can check out" feature doesn't work anymore in satchmo. When it is checked (set as True), I still see the checkout page showing the optional user login and the billing+shipping.
I have tested on my shop and with a newly created store, using the latest satchmo code from https://bitbucket.org/chris1610/satchmo on Mac and Linux Ubuntu 12.04 (server and desktop).
I have checked that the config_value('SHOP', 'AUTHENTICATION_REQUIRED') returns true from the shell. It definitely goes to the redirect function, but it seems that the redirect doesn't work for a reason I don't know. Even forcing the redirect to '/checkout/mustlogin/' doesn't work here, while creating a new page with this redirect works perfectly.