As long as it's as simple to "use and forget" as Dropbox is, I'm happy.
For some reason, never got iDisk to work properly across my Macs/PCs/iOS devices-it just didn't feel right, even though the pieces were supposedly the same.
Dropbox is so transparent in how I use it, it is like second nature. I think Cloud stuff has to be like that to succeed. Plus the security of knowing I have copies on my machine clinches it.