In my opinion, WPML is the most powerful Wordpress multilingual plugin. WPML has a complete startup guide for new users and its side-wide navigation adds top navigation with drop down menus, breadcrumbs trail navigation and also sidebar navigation. WPML is rather too powerful for a simple multilingual website. You can have a lot of options and configurations through the backend admin menu. Adding a non-support language is not that easy. For example, when I tried to add a language which is not supported by default, I need to go to my MySQL backend and manually add in the SQL queries. Hopefully future version will make this easier.