One small update, sometimes the SUS server isn’t detected by just putting the address of the SUS server into the server location in the GPO. You sometimes need to add the default port of the SUS site that’s automatically created in IIS. For example, the default port is http:// wsus:8530, so you’ll need to put that in there instead of just http:// wsus. I discovered this when my SUS server was Server 2012 and IIS 8. I hope this helps some of you.
For the visually oriented folks, I took some screenshots of what I was talking about here:
http://danblee.com/wsus-not-detecting-clients-and-not-listing-computers/