That looks pretty complex, and I don't really want to go messing with the code in my vBulletin app. Also, I checked out Chuck's Reeftalk and even there, when you click Register on the reviews section it takes you to vBulletin's registration page and presents you with the Forum terms of agreement, not the Reviews one.
I really want two completely seperate areas, with different logos (i.e. ****Forums and ****Reviews, but sharing the same user database.
I think I may just keep them seperate. There are a few good reasons too:
1) I don't think my users would appreciate being automatically registered to a part of my site that they may not wish to use.
2) If I want to send an email to the users of the forum, then even people who don't use the forum will get an email.
3) Users may not want to associate their forums username with the reviews section, and vice versa.