Need basic integration -- will 6.x work as is?

sf_user provides this functionality, but afaik does not automate the export/import process.

Install salesforce module and enable salesforce_api and sf_user.
You'll see a SalesForce tab on your /user/% page(s).
This tab will provide the export/import functionality you're looking for, but, like i said, doesn't automate it.

There's a feature request in for this, #411060: sf_node and sf_user need import/export functions for more cck field types., and I agree that it's pretty essential for the usefulness of this module.

al.ex found a great solution that will leverage the node synchronization and User / Contact records:
use content_profile (or a module of your choice that implements user data as node).
From there, you can set up a mapping between your profile node and SalesForce Contact record,
and walla, you've got your integration done without any coding and minimal headache.

On second thought, i don't think this is closed.
I'm marking this postponed, pending the issue mentioned above, #411060: sf_node and sf_user need import/export functions for more cck field types.

Let's track that issue in just one place.