anyway pmw3360 is overkill anyway. its only called 'the best' because it has highest max speed and no flaws. other sensors with no flaws shouldnt be called 'outdated' just because they have a lower max speed.
Its fairly new actually, it is true, but only availiable in Japan. You can order it off of amazon.jp I think though. If you like the Sensei, this would be a great upgrade. Dpi goes in intervals of 50. It has a 3320 sensor.