I've tried them all. The components that have been around a long time for other versions of Joomla (1.0 onwards), and those that emerged after Joomla 2.5 appeared.
We're in Canada, and many organizational sites must be bilingual. And every article must have a alternative language option. And most organizations expect that choosing alternate language will display the same article, just in the other language.
Menus in each language must have the same structure too.
And with the introduction of Joomla 2.5, this became a night-mare to manage, since there was no way to confirm that alternate language menu and category/article structures were the identical, especially when you get into a sites with many menu items, and hundreds or thousands of articles.
I was on the verge of wondering whether there was a future for multingual management in Joomla 2.5+
Then, I discovered KM FasTrans. Whoa! Hold the horses, we have a winner here! It still uses Joomla 2.5's multilingual model, but all of a sudden I have control over the chaos!
I can match English and French categories, menu items, and even articles 1:1 (or default to many). And Joomla will flip between articles even if they aren't associated with a menu item (a big fail in core Joomla 2.5).
KM FasTrans uses some pretty nice tricks to help users narrow down possible items that a default item might link, making life nice and easy.
I tried out with the Free version, and the tech support was amazing with helping work out a bug that I was experiencing, providing a patch within 3 days! There's other extensions where I've waited months, and never even had an acknowledgement back.
Right after the patch was installed, I upgraded to PRO version, and now I'm deploying on several sites right away.
As far as I see it, KM FasTrans has brought multilingual support back to Joomla 2.5!
Go for the PRO version, it the one-click creating of the non-default language items, you'll wonder how you ever survived without this component!