Right now this is my bane. I have been growing used to AD to create illustrations and graphic assets, and the worst thing a client can ask me right now is "Can we have the .ai files?" I export to .PDF, open in CS6, it doesn't keep the layers I had organized and labeled. It also converts the lines to shapes which wouldn't be so bad except they're terribly optimized and have hundreds of points. EPS is a joke, it doesn't even keep the artboard's original size. SVG stares blankly at a wall, shrieks and falls to the side like a fainting goat. I understand you can't do anything about AI due to it being a private format, but these export options need some work.