MSDN has an article on the Web Part Packaging tool (Wppackager). A developer on my staff took it for a whirl today.

Having an MSI for the web parts will be critical for us. With a server farm, the content must be replicated on all the servers. For standard ASP.Net applications, I can use the Distributed File System service to synchronize folders on multiple servers. (And it works very well!!) But with the web.config entries and web part resources, it will be more complicated for WSS sites.

My first impression (as the guy running the install, not the one creating it) is pretty good. One of the resources was not included (a file that is loaded via a SCRIPT tag), but I don't know whether it's a build problem or an install problem.