Can I use the Microsoft Web Platform Installer to install an application that I create? Everything I've seen/read so far seems to indicate it can be used to update IIS, download components as well as free software like WordPress etc. but I haven't found anything to indicate I can use it as a deploy tool for software I make.
Yes, you can upload your app to the gallery but there are a couple of caveats. From Scott Hanselman's post on this topic: