I was definitely one of them. After reading some things online I'm not sure I'd do it for a client in a production setting but, for our own internal and testing purposes, we wanted to run FMS 13 and host some websites from the same box. Oh - and we also run the Rumpus FTP server (which includes a web interface) from that same machine.
The problem of course is that FMS 13 takes over ports 80 and 443:
From FileMaker® Server 13 Getting Started Guide, page 72
In fact, the FileMaker Server installer creates its own instance of the Apache web server on both the master and worker machines and configures this web server to use port 80 for HTTP and port 443 for HTTPS; on the master machine, the installer also configures its Apache web server to use port 16000 for Admin Console via HTTPS. If you have enabled the Apache web server that is already installed with OS X, the FileMaker Server installer prompts you to let it disable any existing website using port 80 or 443 before it can continue.
The documentation goes on to say that you can re-enable other non-FileMaker HTTP services as long as you configure them to use different ports:
If you have the OS X Server application installed and use it to enable any HTTP services (for example, websites or the wiki), the existing Apache instance may be re-enabled after FileMaker Server is installed. Therefore to ensure the Apache instance used by FileMaker Server works normally, you may need to configure any other HTTP services to use different ports from the ports that FileMaker Server uses, disable other HTTP services, or uninstall the OS X Server application.
That sounded easy enough but we had a tough time getting all of the services working at the same time. After a certain amount of frustration we went looking for help and found a really talented OS X Server specialist (Dario) that was able to get things working the way that we wanted.
In the end FMS 13 uses (among others) ports 80 and 443, the web interface for our Rumpus FTP server uses port 8000, and we're hosting some non-FMS stuff on ports 8080 and 8843.
Dario wasn't familiar with FileMaker Server but he got it working satisfactorily on the first try. The only issue was that, when trying to get to non-FMS websites on that server, we had to specify the ports in the URL (like www.example.com:8080). It was fine given that the sites in question really just for testing and internal use but we asked Dario if that could be changed and he made it happen - we no longer had to specify the port number.
That worked very well. The only little thing was that the 8080 would still appear in the url window. We didn't have to specify the port but it would still show up and look a little unusual. Again - absolutely no big deal given what we are doing with this server.
Dario didn't like it though and was able to change it. We're now able to browse sites on port 8080 without seeing any difference. More importantly the entire setup seems very stable and reliable.
I can't tell you how much time, energy and frustration Dario saved us. He was great to work with and very affordable. If you are interested in this type of setup I'd encourage you to visit Dario's blog or check him out on eLance.