Edge), the answer should be pretty obvious: games. "Gameplay is the feature used by most (84 percent) on the PlayStation Portable."
Who would've thunk that a portable gaming device would be used ... well, for games? Although Sony constantly touts PSP's other features, they're still not used by a majority of PSP owners. "Slightly more than one third of PSP owners are watching movies (35 percent) and listening to music (33 percent) on their device." That's a large percentage, but it's certainly far from the majority.
It shouldn't be surprising PSP has lost its luster as a media player; there are certainly much better music and video players out there. While Sony could spend their efforts in improving these features in firmware updates (we wouldn't mind), it seems like Sony should refocus their time on the main thing PSP is meant to be used for: games.