OS X Lion has a hidden 'drop box' for easy file syncing between Macs
tuaw.com
tuaw.com
iCloud
5GB free, 10GB: $20/yr, 50GB: $100/yr
Dropbox
2GB: free, 50GB: $120/yr, 100GB: $240/yr
Since Dropbox is both free for 2GB and rock solid why wouldn't you just use that? (And there is an iOS client too.)
I'd love to use Dropbox to replace my current Windows file server which has about 5 gigs of data accessible to about 50 users. But by my math, that would cost at least $5,000 a year.