I saw your short demo at BarCamp and I must say Dropbox looks great! Are you planning on having a Linux port as well, or is too early to talk about that?
Also, as another SFP applicant I have to tell you that I really hope you get the funding - you deserve it.
a linux port is doable (mac will come first) -- everything's written in python and was designed from the outset to be portable. although this isn't the initial focus of dropbox, a linux port would be interesting for maintaining small web sites or web apps -- instead of using scp/sftp or equivalent you could just modify the files on your desktop and have them synced to your web host.
The app looks great.
Congrats on a great product. A linux port would be great for servers - I'm always rsyncing stuff between my linux boxes.
For those who don't have shell access though, it would be cool if you integrated the service with (S)FTP. I don't even think you'd need to sync to the server.
Just giving the user the ability push his/her dropbox public folder to a server using (S)FTP would give your software several new use cases.
In short, I guess I'm curious what separates Dropbox from using a free FTP service which is connected either through Windows' built-in Network Places or Linux's curlftpfs. There are obvious differences, but are they enough to warrant fees?