Yep that's the plug-in. It's the most 'popular' e-commerce solution (not the best by far, though) so having compatibility would be fantastic (although I've read trying to get other plug-ins to work with it is a bit of a nightmare). Shopp, too, while you're at it :P
I basically need to have product reviews for individual products.
Think of the Apple App Store: There is a an accumulative rating above individual comments for each app, and those comments have their individual ratings displayed as well. If I could have something like that; that would just be epic. Having the option to change the number of 'stars' might be helpful too (e.g. X/5, 10, 20) but it's not something I need at this time, could just be useful in the future.
Could also be out of your scope too :).
Those products are tied to a post type 'wpsc-product', so as long as you could just apply them to a post ID or post-type or whatever then I would basically be set.
It's good to know you are working on it to allow per-product reviews and it's easy to implement. Can't wait :D Thanks for your feedback!