django-multilingual-ng is a branch of django-multilingual and it is compatible with Django 1.2 as well as providing admin UI improvements.
multilingual-ng tries to be compatible with django-multilingual whenever possible. In the best case you can just replace django-multilingual-ng with django-multilingual without having to change any code in your apps.
Note that since multilingual-ng does not use language_id's anymore, you'll have to use the mlng_convert command to migrate your old apps to ng. For this you need south installed.
I'll write documentation once this project hits a somewhat stable level.