Apple Mavericks missing the ball completely…
… behind firewalls.
I'm in the Medical Center of Freiburg University, and that is protected by a firewall, as appropriate. All connections go through proxies. That is standard. What is sub-standard is Apple's approach to this – while there are proxy settings in the network prefpane, they have numerous problems, e.g. sometimes changing by their own free will. What's worse: many services don't seem to respect the firewall at all. With Mavericks, it has now become so bad that you cannot install the system AT ALL behind the firewall! As a student of mine found out: initally use a smartphone for hotspotting, connect with Apple ID, from then on one can install behind the firewall. Incredibly! It gets worse: once you have the system up an running, every 2nd minute it asks you for proxy permissions, id, password, although that's correctly set in said network prefpane. Impossible to work under such conditions. What are they thinking? Are users behind firewalls an irrelevant clientele?
As my student (thanks, David) found out: the Apple fora are full of this, and “Proxifier" was mentioned as a solution. Luckily, that software has a month trial phase with full functionality. After twiddling with proxy rules, things now work as smoothly as they should. So we bought 10 licenses. Sigh, why not out of the box?