There are certainly many ways to achieve this in Ubercart, and again you should remember that products are what Drupal calls nodes. They are pieces of content which may be altered or added to by any number of other modules in Drupal. Some of these are voting modules that let users rank nodes, much like we have enabled for our Live Sites directory. A recommended combination for product reviews is Drupal's core comment module combined with the Fivestar voting module which gets a lot of use in the Drupal community. This in turn depends on the Voting API module. Refer to these product pages for installation and configuration help. In particular, http://drupal.org/node/1308114 gives step-by-step instructions of setting up rating on any content type.
One user has reported success using the Quotes module to have randomly chosen product reviews / testimonials show up on most pages.
For more information, you can review this thread in our forums.