I’ve been using DropBox for about a year now, and it’s a great piece of software. I have had no problems syncing my two Macs, and most recently my iPhone.
DropBox has allowed me to have an offsite backup of my files, with the ability to work on them on either of my Macs, or when I’m away from either of my machines. I can also view files in a pinch from my phone. This is just great software!
My favorite feature is the public folder. You can add any file in this folder, then right click on the file to copy a unique public URL to that file. This URL can be shared via email, website, or social network. A very handy way to get a file out there without having to manually FTP a file to my webserver.
DropBox is free, for 2 GB of web space. If you want to check it out, follow my referral link. Every referral gets you an additional 250 MB of space!