Multilingual websites- one menu for each language or one menu for all languages?
You have a lot more flexibility when using one menu for each individual language. It's a bit more work to setup but it definitivly pays out in the long run.These are the points that are blocking me for using one translatable menu: 
You're not able to reorder menu items for only one language.
You can't deactivate one particular link in one language, the content needs to be disconnected from the link.

Bottom line is when you're sure that you have a fixed menu that doesn't need flexibility it's OK to use i18n_menu.
When building a site that could be expanded in the future and has differences between language content avoid the use of i18n_menu and set up a menu for each language.
(You can set a fixed language in order to do some ajax magic and only show the menu items available for each language when creating new content.)