...Its super easy to use, and is fully automatic - your users don't need to do anything.
So what does it do? Well, it checks the version of the application currently installed against the one on your webserver. If they aren't equal, the updater will run. Its lightweight, and takes just a few seconds to update the software (excluding download times).
UpdateSharp is free, but I ask that you link back in your About box or something.
I have an update planned, and it will happen soon :)
If you get stuck, check the readme file.