Requirements are quite simple: sync up a shared folder between 3 macs, 1 pc and 2 laptops. OS are: Windows XP, Vista and MacOS. Data doesn't need to be on the cloud, but the sync needs to work reliably (dropbox messed up few of the syncs in a bad way and I had to get the backups out)

Data growth is quite slow, may be ~2 Gb/week

I don't have a full time IT person, so I should be able to manage things without going into system administration, rsync scares me

I want to pay may be < $.20/Gb, dropbox is expensive at $.50/gig on their highest capacity plan.

From what I can see AeroFS would fit the bill very nicely, but they seem to be not really available at this point

Another option I am looking at right now is Microsoft Live Mesh, which has an app for a Mac. I don't have ideological reasons not to try them, so I am installing it on one of the macs to see if it works or no

good point, need requirements.

i think bang for buck would be something akin to usb disk, it's arguably offsite. there are lots of software applications that can provide automation of file backup.

if you want sync, there's sugarsync and box.net, haven't used those so no feedback.

if you want online backup there's carbonite and mozy that offer unlimited accounts.