It's for a site that will have both a store and a forum (and probably other stuff). The forum's use wouldn't be limited to posting product reviews (built-in feature of osCommerce), but would be used for product support, general discussion, etc. The reason for integrating them is so that the site will have a consistent look, and a common registration/login.
There's an existing product that integrates phpNuke/osCommerce/phpBB, but I thought I'd try to find a UBB.threads solution if possible.
Right now, I'm thinking of putting UBB.threads in the middle, with "boxes" on the sides. That look would fit in with both IIP and osCommerce, with some tweaking of style sheets and templates. The forum might look too "scrunched up" that way, though.