discourse
Arguably, Syncany is both more standard and has more of the Unix nature given:
- It's Free Software
- Is provider-independent (can be self-hosted)
- The storage server can be fairly "dumb" (i.e., don't need both specialised server and specialised client).
This is another project where I'd really like to contribute (I want to write an Android client, which shouldn't be too terrible given the main project is in Java), but where I don't have anything like the time needed to do it.
SparkleShare is the other main competition: it's possibly even more Unix-y in that it uses git as its backend. And there is an Android client, though I haven't had time to try it out yet.
-- jfm
Despite being a dvcs/git nerd of the highest order, and really liking the idea of all these git-based Dropbox-like replacements, the truth is that I find it really hard to let go and trust some other system to manage my git repositories correctly.
And to be honest, the really killer feature is the app on the Android devices, and then--as a result--the other apps on the phone that connect to Dropbox. Heaven.
There are a lot of problems with this, and I hope it's clear that I'm trying to not gloss over them, but I think the dead-simpleness of Dropbox, combined with these mobile apps that just work. It's worth something.
-- tychoish
Apologies for the ridiculously late reply here; my feed reader expires stuff after 30 days, and so I usually end up seeing stuff a month late. 
My main (desktop) use for Dropbox is synchronizing a git repository. I have two Linux machines I regularly use for my (academic) work, along with a flash drive I use to do work on other computers (Windows machines in a lab). The repo lives on Dropbox, in its non-bare, checked-out glory. As long as I don't try to do git operations while in an unsynchronized state (an easy constraint, as I am but one man), life is good. The flash drive has its own clone, which I commit to and pull to/from.
Why not just do the "normal" git workflow, without Dropbox? I don't always have good network connectivity in the field, and when I do, I don't always remember to take advantage of it. This allows me to commit something, knowing that it will eventually propagate to the other machine. Also, I can manipulate it from arbitrary networked machines (my Android device, lab computers, etc) without git tools, and commit the modifications later on.
My other main use is password database storage... I use KeePassX to store my passwords in a passphrase-encrypted file within Dropbox. Again, it's a synchronization thing. Being able to access this from my Android phone is damn skippy. (Why not use something like LastPass? My current system works just fine for my needs, and pre-dates LastPass.)
I also keep data sheets, manuals, etc in there, but that's probably normal stuff.
Why Dropbox and not something else? I think it's the seamlessness. It synchronizes damn near immediately, the files are stored locally (no network delay), it's multi-platform, and it works on everything I have. It's also cheap and easy. This has been a really hard thing to beat. I haven't looked at Syncany yet, though.
-- Hoo Pycat