Level5 the shopping cart framework which we built has been going on powering heaps of new websites. We landed a huge project with Level5 which have multilingual content (English, French, German, Spanish). So we had to do some enhancements to the Level5 project, in order to accomodate the multilingual content.
Level5 is not just a shopping cart system, we call it a cart framework, which helps us to build different types of e-commerce systems to our clients. It contains two different methods to manage products of the cart. The cart can have dataobjects as products (which can be edited via the model admin) or it can have sitetree types as products (can be managed via the sitetree). In this case we made the multilingual content possible with making the products dataobjects and pulling out the content to sitetree types, which is liked to a specific product. We wont go much further into details with the technology though.
But one more achievement for us we have enabled i18n to the Level5.