Providing you are not intending to use CWP, IWP or PHP, then you can skip this.
You can add this later if you choose. You will need to install all the basic IIS components (plenty of info on Google for a standard install) and then run the web deployment from with the admin console.
The major problem with IIS is if you ever decide to uninstall FileMaker Server (as per the last update). If you have any other web sites configured, the uninstallation process will trash your IIS setup. There are quite long and lengthy procedures that need to be followed to allow you to restore your IIS configuration to the pre-uninstallation setup.
Hope this helps
... time to get a Mac ;-)
Horses for courses Lyndsay ;-)