My SimplePress installation is at 4x4freelanders.org
With WP and SP privileges, you can set different permissions for each section of the site. On WP, the user can be effectively a read-only user (Subscriber). On the SP side, that same person can be a poster.
Now might be a good time for you to set up a test site to see how this stuff works. I actually tried bbPress on the above site and it just didn't fit in as well as I'd hoped, so I went with SimplePress.