Seriously. I left a comment on the host blog observing that points 2, 3, and 4 are basically the same, and can be summarized as: it's insanely easy to use. I set up Dropbox in about 20 seconds, and it did exactly what it said it would. Compared to every other synchronization tool I've ever used, Dropbox wins not by meters, but by miles.
Dropbox works fantastically well with Keepass, just save the .kdb file in your Dropbox folder. Open up Keepass on another system and there are all your password once you wenter the master password.
I'm probably preaching to the converted, I'm sure most people who frequent ycombinator know about that but I still thinks it's once of the best uses for it so far along with backing up critical files.
It's also one of the only online services where I actually am strongly considering subscribing and paying money to upgrade once I approach the 2GB limit.
