The seriously bug fixed Optimal Sync(as of now at 0.8.3) is about to be installable on Windows as well soon. I have started building an .msi-package, which turned out to be a bit more problematic than expected. However, I think I have overcome most of the problems.
So much, actually, that I have felt compelled to poste a guide on how WiX works and its caveats. The guide is thought of as a primer before you get into the official tutorial, which is a bit wordy and difficult to get.
I consider the problems I encountered quite typical of what most that develop an .msi-package encounters and that my example file is more useful. Especially, I use the paraffin.exe-utility instead of the quite insufficient heat.exe . I would imagine that most does, maybe the article can save them some time.
Anyway, the guide is at the wiki, here, and I hope it will help you understand WiX and its somewhat maddening quirks a bit better.