Ask HN: What sync software do you use?

I have a development folder called /htdocs on one computer. I would like it to sync with a folder called /www on another computer. I want this to happen as I make changes, not once a day. I want to sync all files, regardless of the size.

I've tried Jungledisk, Nomadesk, Dropbox... They all require that you move your files to their sync'd folder. I'm looking at Windows Live Sync but it's limited to 20 folders. There seem to be 4 dozen sync products, which one do you swear by?

Thanks!