It has been a while since I last wrote about Ubercart, but I'm still working on some multi-lingual stores for clients. I have opted for disabling the stock Catalog module and using Views instead since Views is so much more flexible and easier to theme. I have a very simple setup; some terms in a vocabulary that is localized per-term, and then a custom View that takes a term name as an argument and returns nodes belonging to that term and displays them in a nicely themed grid.
Recently, I ran into an irritating issue where the View would return results from the wrong language if two languages had the same term name. After hours of investigating (and learning all about how to implement View handlers and plugins), it seems that the stock taxonomy term argument validator for Views cannot differentiate between terms of the same name in different languages. So if multiple languages contain the term "Stewart Adam" for example, the view will just returns nodes for whichever term (and therefore language) comes first in the database query. To be fair, the i18n module adds the "language" column to the term_data table so it's not really View's fault... Nonetheless, I was surprised that the i18n module had not already corrected this issue.
I've just reported Drupal issue #832100, Taxonomy term argument validator should not validate terms defined in other languages that includes a fix to the problem by limiting query for term names to terms within the active language. It's not the greatest way to go about solving it since it essentially just copies the original validator and makes two tiny modifications in the SQL query, but it's better then modifying the View module directly.