Do you control the server side of this scneario. In other words, do you need to use FTP?
The IIS team has developed a technology which should be much better for doing incremental publishing/syncing. It call the Web Deployment Tool. It can be used to sync incrementally over HTTP. The server side of the equation is either a standalone agent service or the same service which IIS 7 remote administation is hosted in.
Any ways, this may be totally non-applicable to you. But if it does apply, checkout the downloads page and the forum.
(Visual Studio 10 will contain integration with this, as has already been demonstrated in their recent tech preview)