I was having trouble recently getting customers through to the checkout page.. the link to the shopping cart took them to an access denied page. 

I set things up according to the video which was great by the way.  I thought that was it and I was finished. 

I discovered that I also needed to configure the permissions for separate user roles...  should have thought of it sooner. I am just  mentioning it so that you could include some mention of that in a future tutorial.  Permissions needed were for the ms core and membership suite... I have medium experience with drupal so figured it out on my own and was fine but a more explicit mention of the permissions might help less exerienced people.