I just learned about Cubby, which is intended to be a DropBox competitor from the folks who did LogMeIn and Join.me. They have one game-changing feature over DropBox that intrigues me: you specify which folders should be synced to cloud storage and which should be only synced directly from computer to computer. The storage cap (initially 5GB) only applies to the cloud storage and not to the direct computer-to-computer folders.
A drawback is that the mobile apps only sync via cloud, so you can’t access the other shared folders. But that’s not unreasonable given the unlikelihood that you’d want to sync more than about 5GB to your phone.
I haven’t actually tried Cubby. I’m just intrigued by their FAQ and features list so far.