It sets up an "X" drive on your local disk, which is exactly the same tree and files as your remote server. We use HomeSite and log in to the sets of files we routinely update on "X", make any changes and hit "save," then it is immediately saved on the server.
Homesite supposedly has built-in deployment, but it doesn't provide the reliability across several servers like WebDrive.
I think it is certainly worth a look, and is in the top-3 of our productivity add-ons.
<added>Since we are always 'live' to the various servers, we do hourly scheduled backups via HandyBackup to the local machines.</added>