Price. It is the most expensive gaming console on the market and thus not the most accessable to those who cant afford to blow that much money on a system yet. I will sneak in a second, it has weak launch titles.
In comparision. Its number one best feature is its open ended system approach where the user base will supply content, games and programs (or overall media) for it. Sneaking in a second best part is its hardware (gpu,cpu,br-rom).