all of the checkout pages should be on the ssl server.
[quote]s there any point to making the user registration page(s) https? [quote]
that is dependent on the type of information you re collecting at registration. If there is no truly sensitive data, then no, you dont really need to have the registration page behind the ssl server.
If your registration page includes setting a secret question, such as mothers maiden name, then yes, you would want it behind the ssl server.