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.
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?