I don't learn a new lang atm but I've heard it works great for that.
There are shared decks [1] and you can create your own very easily. Whenever I stumble over a new fact throughout the day, I (try to) add it to my deck. To test the system, I learned all european countries with capitals and all US states in 4 hours total (spread over weeks, just 1-2 minutes spent every other day). It's really easy and fun.
I use both the desktop and the mobile apps, they keep in sync.