Re: Integration of established WP and BBPress installations
This sounds reasonable but painful. 
Some tips:
* Only upgrade bbPress to 0.9
* Upgrading to WordPress 2.7.1 almost made this impossible, but ck and superanne saved your bacon with plugins for WP 2.7 <=> bbPress 0.9 cookie compatibility.
* Don’t forget to assign your WP users privileges (e.g. Keymaster) by adding a row to the usermeta table
* How are you going to handle user_id conflicts between bbPress and WordPress? For instance, if the WordPress “asdf” user/author has a user_id of 17, and there’s also a user on bbPress with a user_id of 17, you’ll have to do a bunch of UPDATE queries to wp_posts (post_author field) and wp_comments (comment_author and user_id), because when you create a new author with a user_id of 1000, it won’t match up with the post_author_field (etc.) which will have the old 17 number in it.
* Also what about username conflicts, e.g. two users named “asdf”, etc.? That might result in more UPDATE queries… You’ll have to rename the WordPress user, probably.
* The benefit to integrating the databases completely is you don’t have to make two connections to two databases. I’d go for it.
* That extra index on user_nicename is the least of your problems.
* Are you sure that bb_users and wp_users has the exact same database schema? Confirm this! Also, make sure to add any “missing indexes” that are currently in wp_users to “the new wp_users”.
Good luck!
