I've been watching AeroFS for a few months now, and it is a fascinating product that almost meets my needs. Just a few things keep me from using it, some of which I can't quite put my finger on enough to turn in to real feature requests on UserVoice.
- It crashes sometimes. I think it does this less frequently now, but its favorite time to crash is when I suspend & resume my laptop.
- Synchronization is a difficult problem to solve, and users need to have confidence that the software Does It Right. Somehow Dropbox achieves this, and I can't put my finger on how; I think part of it is the fact that conflicting files are duplicated and clearly marked. I haven't had conflicting syncs yet with AeroFS, so I'm not sure how it handles them, but I also haven't seen documentation on what happens. It's a combination of an algorithmic problem, which you presumably have solved, and a UI problem to demonstrate to the user that their data is safe and correct.
- It doesn't yet support ignores. There's a feature request for this, and I've upvoted it, so hopefully it's just a matter of time. When I'm syncing a source directory, I don't want the built files synced. Yes, there's version control, but it's really convenient to sync portions of my Eclipse workspace so I can transparently work on the same changes on both my laptop and workstation.
- I don't know how it works. There are two pieces of this that are interesting to me: the network topology and the crypto design. One of AeroFS's selling points is that your data is never shipped to the centralized cloud unless you explicitly use AeroFS cloud storage. However, as a privacy-conscious user, I would like to know exactly where my data is going, when, and how it is protected. Some data seems to be going to AeroFS's servers for coordination; what all data is? File lists, or just peer locations & names of libraries? A diagram what network connections are used and where data is shipped would help users such as myself understand where our data go and what the risk points are. Hopefully this can be documented without jeopardizing your special sauce/value-add. For the crypto side, it would be useful to know exactly what crypto algorithms are in use, where, and in what configurations. Some providers claim Great Crypto, and then they're using Blowfish. You've got some of this - your Features page discusses the use of the 2048-bit RSA keys. But how is the "secure channel" established? How are the RSA keys secured against theft (e.g. the Dropbox steal-the-auth-DB hack)? The crypto documentation could be overlaid on the network infrastructure documentation. In short - why should I believe the security claims? With things like this, I think extensive transparency is the best way to engender trust with your users, particularly when your competition is criticized for transparency-related issues (e.g. the encryption "misunderstanding" with Dropbox).
I think AeroFS has a lot of promise, and I want you guys to succeed. We need some good, secure, strongly-privacy-preserving competition in the cloud file sync space.