I wasn't talking about including it as standard, but not releasing it as a peripheral. According the Archer MacClean, the tilt sensor was finished and working, and made the 'true' experience of Mercury, yet Sony haven't released it. If they had, PSP would have had a more compelling alternative game experience available and a useful extra for other software.Well Nintendo decided to not include a tilt sensor in the DS too for cost reasons but it doesn't seem to affect DS's popularity. I think not including the tilt in PSP was a smart move from an economic perspective. Not many PSP games would benefit from a tilt sensor.