It's pretty much known that publishing to a remote location using VS2008 is a an exercise of great patience and faith.
As long as a 'publish' begins (using VS2008, publishing an MVC site), that site might be down from the first file that is successfully transferred. The problem being that unreliable internet access, or interesting error messages () can break the site, and require restarting.
It's understood that there is little to do from the VS2008 end. The question then:
What strategy can I use to ensure that there is an acceptable user experience during the 'downtime'? (e.g. "This site is currently under maintenance...")
A lovely feature of ASP.NET/IIS is that if you place a file named app_offline.htm in the root of the web application, all requests will redirect to that file. This would include requests for images, stylesheets, scripts, etc.. so you'll need to condense all media for the page into the page itself.
In fact, while Visual Studio is in the process of publishing your web application, it will place this file in the root of the application and remove it when the publish is complete. While Visual Studio doesn't allow you to customize the contents of its app_offline.htm, you can take the application offline yourself simply by uploading that page.