the S9 handles sound files very well, ID3 or just file browser. It resumes when you stop playback. Video is decent with the screen, i often watch series while on the train. PDF isn't supported, the whole UI is flash based, and depens on flash-apps. stopwatch or timer are no standard apps, but can be easily downloaded and installed (drag and drop). The UI is fully customizable, and responsiveness of the screen is really great. I don't know about the O2, never had a chance of using one..
I'm on a seafood diet, whenever I see food, I eat it