First, let me say that I love Bogo. I think your approach to making a bilingual site with WordPress is great. I have used Qtranslate and have been afraid of the custom tag approach and I think using locale is smart.
I have been able to localize a site with English and Japanese almost completely with Bogo 2.0.1 on WP 3.5 using the Twenty-Eleven theme and a child theme of my own with conditional code like this:
<?php if (get_locale() == 'ja') wp_nav_menu( array( 'theme_location' => 'primary' ) ); else wp_nav_menu( array( 'theme_location' => 'primary_english' )); ?>
This works great for pages but I run into a problem with categories that I am not sure how to deal with. The category name does not change between locales and the category name is what is used on menus, etc. So how do I handle categories using Bogo?
I tried creating two categories and using one for the English posts and one for the Japanese posts. That works OK but when I use the language switcher widget in Bogo it tries to go to the same category name in the other locale and there are no posts to show then...