Worrying about pirates is nothing. They know they pirated it, and they won't openly ask for a key. You usually have those who don't know how to pirate asking for keys.

I'm not exactly sure what you mean by your bitmaps/sounds.map scenario. But if I understand it correctly, why would anyone ever do that? If you want to have two sets, compile them into the same, or just don't reference it as a shared resource and compile that in the map. Shared caches are meant for things that are universal across all maps, such as bitmaps, sounds, music, weapons, vehicles, and UI elements. And regardless, you'll always have a scenario that is either the same size as it would normally be or smaller.

OS could be unstable depending on what you do and who does it. I don't want to speak for Kornman here, but I would assume that something like this is pretty damn stable as long as you use it right. Not really sure how it can screw up and go so wrong when it's just compiling like normal, but splitting resources between two files.