CX allows you to backup your files, sync them across multiple devices, share your files and collaborate on them with others, and even discover new ideas and friends.
A free account starts off at 10GB of storage, which is more that the other services offer. Like the other services, you can earn more storage for referring others to sign up (to a maximum of 16GB). There are also paid plans with more storage (50GB, 100GB and custom amounts).
It is currently available for iOS and Android is coming soon. No mention of other mobile OS's.
What is unique is that every file you share has a comment system so you can share it and collaborate with others on it.
I think everyone needs to use some sort of file backup and sync service. Try CX out.