PlayStation Vita's rear touch panel at first. Speaking to Famitsu (as translated by Andriasang), Sony's president of worldwide studios, Shuhei Yoshida, revealed that the portable's most groundbreaking feature was nearly stricken from the final design due to cost concerns. Specifically, Sony wasn't sure that the effect it would have on gameplay was worth its part of the sticker price.
That changed, though, after people actually got their hands on it; it went from questionable to being a must-have feature. Yoshida said in the same interview that while the touch panel is definitely a keeper, some small elements of the Vita's design are still subject to change. We're guessing he means minor cosmetic tweaks, since the hardware we saw at E3 seemed pretty much final. Whatever gets altered, it'd better not involve removing the ultra-spiffy PlayStation icon pattern on the touch panel.