Gamespot is reporting that over 4,800 PSPs, which is .6% of the 800,000 units sold, have been returned due to defects. It seems that the Square button has reduced sensitivity due to its sensor not being exactly under the button. This configuration is due to the button's close proximity to the screen, and is designed to keep pressure off of the screen.
SCE President Ken Kutaragi said in a recent interview that "The button's location is [architectured] on purpose," Kutaragi added. "It's according to specifications. This is something that we've created, and this is our specification. There was a clear purpose to it, and it wasn't a mistake."
The launch in Japan has been highly successful in many ways, but the continuing reports of defects are nothing new to early adopters of Sony's gaming machines. The both the original Playstation and the PS2 have had their fair share of problems due to poor design.