First time I tried to reach the WCF service it gave me an error that said 'The page you are requesting cannot be served because of the extension configuration.' This means you need to run Servicemodelreg.exe to reregister WCF (same kind of registration you needed from time to time for ASP .NET on previous versions of IIS, remember aspnet_regiis). You can find this tool at C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation for version 3.0 or at C:\Windows\Microsoft.NET\Framework\v4.0.30319 for version 4.0.
Now looking at the MSDN site, they will tell you to run the 3.0 version. After doing so, however, you won't have the necessary handlers installed for a WCF service created with Visual Studio 2012, since they are all version 4.0. So that won't work.
Running the 4.0 version however won't work either. If you try Servicemodelreg.exe -i it will tell you to register with the -c option (register a component). If you try the -i -c option you will get the error (and the solution!) that this tool cannot be used on this version of windows. What you can use, though, is the 'Turn Windows Features On/Off' dialog.
So simply open this up from your control panel (I pinned my control panel to my start page on day one of installing Windows 8, otherwise I wouldn't be able to find it again) and check the necessary WCF features you want to have available on your WCF. In most cases, just flagging HTTP will do. You can find the WCF features under .NET Framework 4.5 Advanced Services.
And that's what you need to get yuor WCF service running under IIS on Windows 8. Hope this was helpful.
Addendum: This fix recently also solved the issue of a 'HTTP Error 400. The request hostname is invalid' error of a colleague when trying to run a WCF service on Windows 8.
