One nice feature is that when you share a folder with others, you get “charged” for only part of the space against your quota.... if you share a folder with one other user, you each are charged for half the space actually used. If you share a folder with 10 others, you're each charged with only 10% of the space. That's nice.
If you'd like to give them a try and sign up via their home page, you'll get the standard 15GB of free storage space.
Of course, you know this is coming: if you sign upwe both get 5GB extra.
That's their logo at right, which I like; they explain it on their “About” page.