I really agree with Dima here-touch is the alpha and the omega of piano technique.
Control of portato is one of the main things that separate today's typical competition winner from the great masters of yesterday-Gilels, Richter, Horowitz, Gould. It's their touch. I want to say it's magic, but it actually isn't; it's just very well-controlled. Their minds are in complete control of the total sound-picture, and it is the touch of the fingertips that translates that mental control into music via the keyboard.
Think how many young players there are out there today who play the notes fast, accurate, etc. but without the colour, nuance, and full range of artistic subtleties that the real masters had.
Watch the great pianists-when they play, it's as though they hardly move at all. Think Michelangeli. You don't see him flopping his arms around the way KBK does. Same goes for Horowitz.